[MRELEASE-1012] Customize SCM changes commit message, not only the preffix

**[Rachide Ouattara](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=orachide)** opened **[MRELEASE-1012](https://issues.apache.org/jira/browse/MRELEASE-1012?redirect=false)** and commented

It's currently only possible to customize the **[scmCommentPrefix](http://maven.apache.org/maven-release/maven-release-plugin/prepare-mojo.html#scmCommentPrefix)** ([maven-release-plugin]) part of a message commit.

It would be nice to be able to also customize the second part of the message :
* prepare release v0.0.16
* prepare release {0}

Many  users asked for that long time ago, but it still not possible.

We could continue to use the default message, but allow developers  to override those messages in the plugin configuration (or as a command line parameter)

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No further details from [MRELEASE-1012](https://issues.apache.org/jira/browse/MRELEASE-1012?redirect=false)

Start with the maven-release-plugin prepare goal and its scmCommentPrefix configuration, then trace where the default “prepare release {0}” message is assembled. Compare plugin configuration and command-line entry points, and consider how existing release flows would verify a separately configurable message template.

Written by the indexing model from the issue text.