[Maintenance] Add spotless options

[devtobi]

Relevant template

refarch-backend, refarch-eai

Problem description (optional)

Spotless has capabilities currently not used (import sorting, removing unused imports and so on)

Desired solution

Add the options

<importOrder/>
<removeUnusedImports />
<formatAnnotations />

I took a look at the currently used https://github.com/it-at-m/itm-java-codeformat/blob/main/formatter/src/main/resources/itm-java-codeformat/java_codestyle_formatter.xml.
Those options are not available there.

Alternatively to the standard import order mentioned above, we could think about a custom import order. An example:

<importOrder>  <!-- or a custom ordering -->
  <wildcardsLast>false</wildcardsLast> <!-- Optional, default false. Sort wildcard import after specific imports -->
  <order>java|javax,org,com,com.diffplug,,\#com.diffplug,\#</order>  <!-- or use <file>${project.basedir}/eclipse.importorder</file> -->
  <!-- you can use an empty string for all the imports you didn't specify explicitly, '|' to join group without blank line, and '\#` prefix for static imports. -->
  <semanticSort>false</semanticSort> <!-- Optional, default false. Sort by package, then class, then member (for static imports). Splitting is based on common conventions (packages are lower case, classes start with upper case). Use <treatAsPackage> and <treatAsClass> for exceptions. -->
  <treatAsPackage> <!-- Packages starting with upper case letters. -->
    <package>com.example.MyPackage</package>
  </treatAsPackage>
  <treatAsClass> <!-- Classes starting with lower case letters. -->
    <class>com.example.myClass</class>
  </treatAsClass>
</importOrder>

Considered alternatives (optional)

No response

Additional context (optional)

No response

No duplicate

• I confirm that this issue is not a duplicate

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• I agree to follow this project's Code of Conduct

[devtobi]

I suggest using semanticSort set to true with

<importOrder>
    <semanticSort>true</semanticSort> <!-- Sort by package, then class, then member (for static imports). Splitting is based on common conventions (packages are lower case, classes start with upper case) -->
</importOrder>

[devtobi]

The new mentioned options are only available in a later Spotless version (see diffplug/spotless#1920) than the one thats currently in use. With the problem mentioned in #16 we need to set this issue to blocked for now.

[eidottermihi]

We used https://github.com/revelc/formatter-maven-plugin before we switched to spotless. It's way more limited than spotless, but at least Eclipse JDT rules from https://github.com/it-at-m/itm-java-codeformat can be checked/enforced in CI without side-loading stuff from the internet as spotless currently needs.