Clean up docker file

This commit fixes up the Dockerfile to make it a bit cleaner and remove some cruft

.dockerignore

@@ -0,0 +1 @@
+target/

Dockerfile

@@ -1,35 +1,15 @@
 FROM ekidd/rust-musl-builder:stable as builder
-
-WORKDIR /usr/src/app
-
-COPY . .
-
-RUN cargo install --path .
-
+ADD --chown=rust:rust . ./
+RUN cargo build --release
 
 FROM alpine:latest as runner
-
-ARG APP=/usr/src/app
-
-ENV TZ=Etc/UTC \
-    APP_USER=appuser
-
-RUN addgroup -S $APP_USER \
-    && adduser -S -g $APP_USER $APP_USER
-
-RUN apk add --no-cache ca-certificates tzdata
-
-WORKDIR ${APP}
-
-COPY --from=builder ${APP}/target/x86_64-unknown-linux-musl/release/gravel-gateway .
-
-RUN chown -R $APP_USER:$APP_USER ${APP}
-
+ARG APP_USER=gravel
+RUN addgroup -S $APP_USER && adduser -S -g $APP_USER $APP_USER
+COPY --from=builder /home/rust/src/target/x86_64-unknown-linux-musl/release/gravel-gateway /usr/bin/gravel-gateway
+RUN chown -R $APP_USER:$APP_USER /usr/bin/gravel-gateway
 USER $APP_USER
-
 EXPOSE 4278
 
-ENTRYPOINT [ "./gravel-gateway", "-l", "0.0.0.0:4278" ]
+ENTRYPOINT [ "/usr/bin/gravel-gateway", "-l", "0.0.0.0:4278" ]
 
-HEALTHCHECK --interval=30s --timeout=3s \
-  CMD wget --spider localhost:4278/metrics
+HEALTHCHECK --interval=30s --timeout=3s CMD wget --spider localhost:4278/metrics