Improve maven plugin tags documentation

See gh-33609

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/docs/asciidoc/packaging-oci-image.adoc

@@ -185,7 +185,7 @@ The value supplied will be passed unvalidated to Docker when creating the builde
 | `false`
 
 | `tags`
-| One or more additional tags to apply to the generated image.
+|One or more additional tags to apply to the generated image. The values provided to the `tags` option should be full image references in the form of `[image name]:[tag]` or `[repository]/[image name]:[tag]`.
 |
 
 | `caches`