Various maven related documentation changes (#964)

* re-organized the maven plugin docs a bit and added some info about "test-update" and file extensions

* incorporate feedback from review

docs/modules/ROOT/nav.adoc

@@ -6,6 +6,8 @@ endif:getting-started/:[]
 * xref:getting-started/assembly-installing-the-registry-openshift.adoc[]
 * xref:getting-started/assembly-configuring-the-registry.adoc[]
 * xref:getting-started/assembly-managing-registry-artifacts-ui.adoc[]
+* xref:getting-started/assembly-managing-registry-artifacts-api.adoc[]
+* xref:getting-started/assembly-managing-registry-artifacts-maven.adoc[]
 * xref:getting-started/assembly-using-kafka-client-serdes.adoc[]
 * xref:getting-started/assembly-using-the-registry-client.adoc[]
 * xref:getting-started/assembly-registry-reference.adoc[]

docs/modules/ROOT/pages/getting-started/assembly-managing-registry-artifacts-api.adoc

@@ -3,16 +3,14 @@
 include::{mod-loc}shared/all-attributes.adoc[]
 
 [id="managing-registry-artifacts-api"]
-= Managing {registry} content using the REST API 
+= Managing {registry} content using the REST API
 //If the assembly covers a task, start the title with a verb in the gerund form, such as Creating or Configuring.
 
 This chapter explains how to manage artifacts stored in the registry using the Registry REST API. This includes using Registry REST API commands, a Maven plug-in, or a Java client application:
 
 * xref:managing-artifacts-using-rest-api[]
-* xref:managing-artifacts-using-maven-plugin[]
 * xref:managing-artifacts-using-client-code[]
 
 //INCLUDES
 include::{mod-loc}getting-started/proc-managing-artifacts-using-rest-api.adoc[leveloffset=+1]
-include::{mod-loc}getting-started/proc-managing-artifacts-using-maven-plugin.adoc[leveloffset=+1]
 include::{mod-loc}getting-started/proc-managing-artifacts-using-client-code.adoc[leveloffset=+1]

docs/modules/ROOT/pages/getting-started/assembly-managing-registry-artifacts-maven.adoc

@@ -0,0 +1,13 @@
+// Metadata created by nebel
+
+include::{mod-loc}shared/all-attributes.adoc[]
+
+[id="managing-registry-artifacts-maven"]
+= Managing {registry} content using the Maven plug-in
+
+This chapter explains how to manage artifacts stored in the registry using the {registry} Maven plug-in.
+
+* xref:managing-artifacts-using-maven-plugin[]
+
+//INCLUDES
+include::{mod-loc}getting-started/proc-managing-artifacts-using-maven-plugin.adoc[leveloffset=+1]

docs/modules/ROOT/partials/getting-started/proc-managing-artifacts-using-maven-plugin.adoc

@@ -12,67 +12,111 @@
 * {registry} must be installed and running in your environment
 * Maven must be installed and configured in your environment
 
-.Procedure
+== Registering an artifact using the Maven plug-in
+
+Probably the most common use case for the Maven plug-in is registering artifacts during a build.  You can accomplish
+this by using the `register` goal provided.  Simply update your Maven `pom.xml` file to use the
+`apicurio-registry-maven-plugin` to upload an artifact to {registry}.
+
+The following example shows registering an Apache Avro schema artifact:
 
-. Update your Maven `pom.xml` file to use the `apicurio-registry-maven-plugin` to upload an artifact to {registry}. The following example shows registering an Apache Avro schema artifact:
-+
 [source,xml]
 ----
 <plugin>
-<groupId>io.apicurio</groupId>
-<artifactId>apicurio-registry-maven-plugin</artifactId>
-<version>${registry.version}</version>
-<executions>
-  <execution>
-    <phase>generate-sources</phase>
-    <goals>
-      <goal>register</goal> <1>
-    </goals>
-    <configuration>
-      <registryUrl>http://my-cluster-service-registry-myproject.example.com/api</registryUrl> <2>
-      <artifactType>AVRO</artifactType> 
-      <artifacts>
-        <schema1>${project.basedir}/schemas/schema1.avsc</schema1> <3>
-      </artifacts>
-    </configuration>
-  </execution>
-</executions>
+  <groupId>io.apicurio</groupId>
+  <artifactId>apicurio-registry-maven-plugin</artifactId>
+  <version>${registry.version}</version>
+  <executions>
+    <execution>
+      <phase>generate-sources</phase>
+      <goals>
+        <goal>register</goal> <1>
+      </goals>
+      <configuration>
+        <registryUrl>http://my-cluster-service-registry-myproject.example.com/api</registryUrl> <2>
+        <artifactType>AVRO</artifactType>
+        <artifacts>
+          <schema1>${project.basedir}/schemas/schema1.avsc</schema1> <3>
+        </artifacts>
+      </configuration>
+    </execution>
+  </executions>
 </plugin>
 ----
-+
 <1> Specify `register` as the execution goal to upload an artifact to the registry.
 <2> You must specify the {registry} URL with the `/api` endpoint.
-<3> You can upload multiple artifacts using the artifact ID and location. 
+<3> You can upload multiple artifacts using the artifact ID and location.
+
+== Downloading an artifact using the Maven plug-in
+You can also use the Maven plug-in to download artifacts from {registry}.  This is often useful, for example, when
+generating code from a registered schema.
+
+The following example shows downloading a single schema by its artifact ID.
 
-. You can also update your Maven `pom.xml` file to download a previously registered artifact from {registry}:
-+
 [source,xml]
 ----
 <plugin>
 <groupId>io.apicurio</groupId>
 <artifactId>apicurio-registry-maven-plugin</artifactId>
 <version>${registry.version}</version>
-<executions>   
+<executions>
   <execution>
-    <phase>generate-sources</phase> 
+    <phase>generate-sources</phase>
     <goals>
       <goal>download</goal> <1>
     </goals>
     <configuration>
       <registryUrl>http://my-cluster-service-registry-myproject.example.com/api</registryUrl> <2>
-          <ids>
-            <param1>schema1</param1> <3>
-          </ids>
+      <ids>
+        <param1>schema1</param1> <3>
+      </ids>
+      <artifactExtension>.avsc</artifactExtension> <4>
       <outputDirectory>${project.build.directory}</outputDirectory>
    </configuration>
  </execution>
-</executions>   
+</executions>
 </plugin>
 ----
-+
 <1> Specify `download` as the execution goal.
 <2> You must specify the {registry} URL with the `/api` endpoint.
 <3> You can download multiple artifacts to a specified directory using the artifact ID.
+<4> The plug-in will automatically try to select an appropriate file extension, but you can override it using `<artifactExtension>`.
+
+== Testing an artifact
+You may want to simply verify that an artifact can be registered without actually making any changes.  This is most
+often useful when rules have been configured in {registry}.  Testing the artifact will result in a failure if the
+artifact content violates any of the configured rules.
+
+NOTE: Even if the artifact passes the test, no content will be added to {registry}.
+
+The following example shows testing an Apache Avro schema artifact:
+
+[source,xml]
+----
+<plugin>
+  <groupId>io.apicurio</groupId>
+  <artifactId>apicurio-registry-maven-plugin</artifactId>
+  <version>${registry.version}</version>
+  <executions>
+    <execution>
+      <phase>generate-sources</phase>
+      <goals>
+        <goal>test-update</goal> <1>
+      </goals>
+      <configuration>
+        <registryUrl>http://my-cluster-service-registry-myproject.example.com/api</registryUrl> <2>
+        <artifactType>AVRO</artifactType>
+        <artifacts>
+          <schema1>${project.basedir}/schemas/schema1.avsc</schema1> <3>
+        </artifacts>
+      </configuration>
+    </execution>
+  </executions>
+</plugin>
+----
+<1> Specify `test-update` as the execution goal to test an artifact.
+<2> You must specify the {registry} URL with the `/api` endpoint.
+<3> You can test multiple artifacts using the artifact ID and location.
 
 .Additional resources
  * For more details on the Maven plug-in, see https://github.com/Apicurio/apicurio-registry-demo.