feat: add generic properties as extension element

[menski]

Description

Allow to specify generic properties as extension elements in the Zeebe namespace.

<bpmn:extensionElements>
  <zeebe:properties>
    <zeebe:property name="name1" value="value1" />
    <zeebe:property name="name2" value="value2" />
  </zeebe:properties>
</bpmn:extensionElements>

This change does not include any getter/setter or builder for properties as we expect them being used mainly by modeler users and have no execution semantic.

Related issues

closes #9868

Definition of Done

Not all items need to be done depending on the issue and the pull request.

Code changes:

• The changes are backwards compatibility with previous versions
• If it fixes a bug then PRs are created to backport the fix to the last two minor versions. You can trigger a backport by assigning labels (e.g. backport stable/1.3) to the PR, in case that fails you need to create backports manually.

Testing:

• There are unit/integration tests that verify all acceptance criterias of the issue
• New tests are written to ensure backwards compatibility with further versions
• The behavior is tested manually
• The change has been verified by a QA run
• The impact of the changes is verified by a benchmark

Documentation:

• The documentation is updated (e.g. BPMN reference, configuration, examples, get-started guides, etc.)
• New content is added to the release announcement
• If the PR changes how BPMN processes are validated (e.g. support new BPMN element) then the Camunda modeling team should be informed to adjust the BPMN linting.

Please refer to our review guidelines.

[github-actions]

Test Results

   803 files  +  2         1 errors  802 suites  +2   1h 37m 51s ⏱️ -8s
6 073 tests  - 65  6 064 ✔️  - 65  9 💤 ±0  0 ❌ ±0 
6 259 runs   - 65  6 250 ✔️  - 65  9 💤 ±0  0 ❌ ±0 

For more details on these parsing errors, see this check.

Results for commit 353a3ee. ± Comparison against base commit c7eccc4.

♻️ This comment has been updated with latest results.

[saig0]

@menski looks all good 👍

❌ But I would like to see an integration test. Since the properties will not be used in the engine itself, we should verify that we can read the properties from a given model. For example, building a BPMN with these extension elements and using the model API to read the properties. Otherwise, we don't realize if we can't read the properties as expected.

[menski]

@saig0 I added a read test, please let me know if you think we should have a bigger/different test

[saig0]

@menski I like it 👍

bors merge

[zeebe-bors-camunda]

Build succeeded:

• Java checks
• Go linting
• Test summary