Implement global HTML injection for head and footer (#9)

#### What type of PR is this?
/kind feature
#### What this PR does / why we need it:
此 PR 实现了代码全局的HEAD和FOOTER注入，暂时没有实现路径匹配的逻辑
#### Which issue(s) this PR fixes:
Fixes #8 
#### Does this PR introduce a user-facing change?
```release-note
None
```

build.gradle

@@ -16,7 +16,7 @@ repositories {
 }
 
 dependencies {
-    implementation platform('run.halo.tools.platform:plugin:2.11.0-SNAPSHOT')
+    implementation platform('run.halo.tools.platform:plugin:2.17.0-SNAPSHOT')
     compileOnly 'run.halo.app:api'
 
     testImplementation 'run.halo.app:api'

src/main/java/run/halo/injection/AbstractHtmlProcessor.java

@@ -0,0 +1,18 @@
+package run.halo.injection;
+
+import java.util.Set;
+import org.thymeleaf.context.ITemplateContext;
+
+public abstract class AbstractHtmlProcessor {
+    protected static final String TEMPLATE_ID_VARIABLE = "_templateId";
+
+    protected boolean isContentTemplate(ITemplateContext context) {
+        return "post".equals(context.getVariable(TEMPLATE_ID_VARIABLE))
+            || "page".equals(context.getVariable(TEMPLATE_ID_VARIABLE));
+    }
+
+    // 匹配路径接口
+    protected boolean isRequestPathMatchingRoute(String requestRoute, Set<String> pageRules) {
+        return true;
+    }
+}

src/main/java/run/halo/injection/HtmlFooterProcessor.java

@@ -0,0 +1,36 @@
+package run.halo.injection;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Component;
+import org.thymeleaf.context.ITemplateContext;
+import org.thymeleaf.model.IModel;
+import org.thymeleaf.model.IProcessableElementTag;
+import org.thymeleaf.processor.element.IElementTagStructureHandler;
+import reactor.core.publisher.Mono;
+import run.halo.app.theme.dialect.TemplateFooterProcessor;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class HtmlFooterProcessor extends AbstractHtmlProcessor implements TemplateFooterProcessor {
+    private final HtmlService htmlService;
+
+    @Override
+    public Mono<Void> process(ITemplateContext context, IProcessableElementTag tag,
+        IElementTagStructureHandler structureHandler, IModel model) {
+        return htmlService.listEnabledInjectionsByPoint(HtmlInjection.InjectionPoint.FOOTER)
+            .doOnNext(htmlInjection -> {
+                if (isContentTemplate(context)) {
+                    model.add(
+                        context.getModelFactory().createText(
+                            htmlInjection.getSpec().getFragment()));
+                }
+            })
+            .onErrorResume(e -> {
+                log.error("HtmlFooterProcessor process failed", e);
+                return Mono.empty();
+            })
+            .then();
+    }
+}

src/main/java/run/halo/injection/HtmlHeadProcessor.java

@@ -0,0 +1,35 @@
+package run.halo.injection;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Component;
+import org.thymeleaf.context.ITemplateContext;
+import org.thymeleaf.model.IModel;
+import org.thymeleaf.processor.element.IElementModelStructureHandler;
+import reactor.core.publisher.Mono;
+import run.halo.app.theme.dialect.TemplateHeadProcessor;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class HtmlHeadProcessor extends AbstractHtmlProcessor implements TemplateHeadProcessor {
+    private final HtmlService htmlService;
+
+    @Override
+    public Mono<Void> process(ITemplateContext context, IModel model,
+        IElementModelStructureHandler structureHandler) {
+        return htmlService.listEnabledInjectionsByPoint(HtmlInjection.InjectionPoint.HEADER)
+            .doOnNext(htmlInjection -> {
+                if (isContentTemplate(context)) {
+                    model.add(
+                        context.getModelFactory().createText(
+                            htmlInjection.getSpec().getFragment()));
+                }
+            })
+            .onErrorResume(e -> {
+                log.error("HtmlHeadProcessor process failed", e);
+                return Mono.empty();
+            })
+            .then();
+    }
+}

src/main/java/run/halo/injection/HtmlService.java

@@ -0,0 +1,8 @@
+package run.halo.injection;
+
+import reactor.core.publisher.Flux;
+
+public interface HtmlService {
+
+    Flux<HtmlInjection> listEnabledInjectionsByPoint(HtmlInjection.InjectionPoint injectionPoint);
+}

src/main/java/run/halo/injection/HtmlServiceImpl.java

@@ -0,0 +1,38 @@
+package run.halo.injection;
+
+import static run.halo.app.extension.index.query.QueryFactory.and;
+import static run.halo.app.extension.index.query.QueryFactory.equal;
+
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.Sort;
+import org.springframework.stereotype.Service;
+import reactor.core.publisher.Flux;
+import run.halo.app.extension.ListOptions;
+import run.halo.app.extension.ReactiveExtensionClient;
+import run.halo.app.extension.index.query.Query;
+
+@Service
+@RequiredArgsConstructor
+public class HtmlServiceImpl implements HtmlService {
+    private final ReactiveExtensionClient client;
+
+    /**
+     * 根据注入点获取正在启用的HtmlInjection 对象.
+     */
+    @Override
+    public Flux<HtmlInjection> listEnabledInjectionsByPoint(
+        HtmlInjection.InjectionPoint injectionPoint) {
+        Query query = and(
+            equal("spec.enabled", "true"),
+            equal("spec.injectionPoint", injectionPoint.name())
+        );
+
+        ListOptions options = ListOptions.builder()
+            .fieldQuery(query)
+            .build();
+
+        return client.listAll(HtmlInjection.class, options,
+            Sort.by(Sort.Order.asc("metadata.name")));
+    }
+}
+

src/main/java/run/halo/injection/InjectionPlugin.java

@@ -1,12 +1,14 @@
 package run.halo.injection;
 
+import static run.halo.app.extension.index.IndexAttributeFactory.simpleAttribute;
+
 import org.springframework.stereotype.Component;
 import run.halo.app.extension.Scheme;
 import run.halo.app.extension.SchemeManager;
+import run.halo.app.extension.index.IndexSpec;
 import run.halo.app.plugin.BasePlugin;
 import run.halo.app.plugin.PluginContext;
 
-
 @Component
 public class InjectionPlugin extends BasePlugin {
     private final SchemeManager schemeManager;
@@ -18,7 +20,24 @@ public InjectionPlugin(PluginContext pluginContext, SchemeManager schemeManager)
 
     @Override
     public void start() {
-        schemeManager.register(HtmlInjection.class);
+        schemeManager.register(HtmlInjection.class, indexSpecs -> {
+            // 为 enabled 添加索引方便根据启用状态查询
+            indexSpecs.add(new IndexSpec()
+                .setName("spec.enabled")
+                .setIndexFunc(simpleAttribute(HtmlInjection.class, htmlInjection -> {
+                    return Boolean.toString(htmlInjection.getSpec().isEnabled());
+                }))
+            );
+            // 为 injectionPoint 添加索引
+            indexSpecs.add(new IndexSpec()
+                .setName("spec.injectionPoint")
+                .setIndexFunc(simpleAttribute(HtmlInjection.class, htmlInjection -> {
+                    HtmlInjection.InjectionPoint injectionPoint =
+                        htmlInjection.getSpec().getInjectionPoint();
+                    return injectionPoint != null ? injectionPoint.name() : null;
+                }))
+            );
+        });
     }
 
     @Override