[7.2] Review subsystem namespace versions, replace with attributes

We have many subsystem configuration XML examples in the documentation. The XML examples contain namespace entries that contain the version of that subsystem for the release. Since these version can change from release to release, we have defined document attributes for many of these namespaces.

For example, we define the following Undertow namespace attribute:

:UndertowSubsystemNamespace:  urn:jboss:domain:undertow:6.0

We use it correctly in many places in our Asciidoc files. NOTE: When using an attribute in the XML example, you need to add the `subs="attributes+"` to the source block.

[source,xml,options="nowrap",subs="attributes+"]
----
<subsystem xmlns="{UndertowSubsystemNamespace}">
    ...
</subsystem>
----

NOTE: When using an attribute in the XML example, you need to add the subs="attributes+" to the source block declaration.

However, using the grep command, you find many instances where the namespace is still hard-coded in the docs.

[source,xml,options="nowrap"]
----
<subsystem xmlns="urn:jboss:domain:undertow:3.0">
  ...
 </subsystem>
----

We need to do the following:

1. Review the latest JBoss EAP configuration files, for example, standalone/configuration/standalone-full-ha.xml, and determine the correct version for each subsystem.
2. Update the appropriate attributes in the document-attributes.adoc file to use the correct version for each namespace.
3. Find all instances of hard-coded namespaces and replace them with the attribute making sure to update the source block declaration with the subs="attributes+". You can navigate to the docs/ directory and use this command to find hard-coded instances in our files: grep 'subsystem xmlns="u' `find . -name '*.adoc'`
4. Add an attribute if one is not defined.