Add resources DSL (#523)

This streamlines configuration of enabling `androidResources` and
enforces use of a resource prefix to avoid conflicts.

May your avatars never be wrongly sized again.

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docs/dsl.md

@@ -65,6 +65,12 @@ By default, SGP disables androidTests in projects. These can be enabled via the
 
 This is important for opting in tests to [AndroidTest APK Aggregation](/utilities/#androidtest-apk-aggregation).
 
+### Resources
+
+By default, we disable _Android_ resources (different from _Java_ resources) and libraries have to opt-in to using them.
+
+This can be enabled via the `resources()` feature, which will enable the relevant `BuildFeature` in the Android plugin and also takes a required `prefix` parameter that is used as the required `resourcePrefix` for that library's resources to avoid naming conflicts.
+
 ## Android Application Features
 
 ### Permission AllowList

slack-plugin/src/main/kotlin/slack/gradle/SlackExtension.kt

@@ -18,6 +18,7 @@
 package slack.gradle
 
 import com.android.build.api.dsl.CommonExtension
+import com.android.build.gradle.LibraryExtension
 import com.squareup.anvil.plugin.AnvilExtension
 import dev.zacsweers.moshix.ir.gradle.MoshiPluginExtension
 import javax.inject.Inject
@@ -813,6 +814,20 @@ public abstract class AndroidFeaturesHandler @Inject constructor() {
     androidExtension!!.testOptions.unitTests.isIncludeAndroidResources = true
     robolectric.setDisallowChanges(true)
   }
+
+  /**
+   * **LIBRARIES ONLY**
+   *
+   * Enables android resources in this library and enforces use of the given [prefix] for all
+   * resources.
+   */
+  public fun resources(prefix: String) {
+    val libraryExtension =
+      androidExtension as? LibraryExtension
+        ?: error("slack.android.features.resources() is only applicable in libraries!")
+    libraryExtension.resourcePrefix = prefix
+    libraryExtension.buildFeatures { androidResources = true }
+  }
 }
 
 @SlackExtensionMarker