[MJAVADOC-799] Remove inconsistent AbstractFixJavadocMojo#defaultVersion default value

[Marcono1234]

As mentioned in MJAVADOC-799 there is currently a mismatch for the AbstractFixJavadocMojo#defaultVersion parameter default value:

• documented value: $Id:$
• initial field value: $Id: $
• @Parameter#defaultValue: $Id: $Id

It seems @Parameter#defaultValue overwrites the initial field value. This can be seen when running mvn org.apache.maven.plugins:maven-javadoc-plugin:3.7.0:fix on a dummy project; it will add @version $Id: $Id to the Javadoc.

As mentioned in the Jira issue I am not sure if $Id: $Id is really a good / the intended default value, but it is the value currently used by the Mojo, therefore I have kept it. And I have adjusted the expected unit test results because they don't seem to create the Mojo instance the way Maven normally does, and are therefore using the initial field value (which was previously incorrect) instead of @Parameter#defaultValue.

I have also included some small changes for URLs and defaultValue for other parameters. Please let me know if I should omit that because it is not directly related to this.

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[michael-o]

Since the value cannot be reasonably set to empty I would drop the default value, it has no use at all.

[Marcono1234]

Thanks for the adjustments! It seems currently no test covers a custom defaultVersion value, unless I am overlooking something. Should I create a follow-up pull request and adjust the unit test or the integration test to use a custom value?

[michael-o]

Thanks for the adjustments! It seems currently no test covers a custom defaultVersion value, unless I am overlooking something. Should I create a follow-up pull request and adjust the unit test or the integration test to use a custom value?

That'd be great. Currently, we cover that there is no default value for defaultVersion. Now we need a test with a custom version set and that the version truly arrives in the modified files.

[Marcono1234]

Have created #305 for adding a test.