Fix GraphMetadata serialization: attributes' order

[olperr1]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem?

No

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

On some systems, the export order of GraphMetadata attributes is determined by the order of the 1st encountered JsonCreator's attributes and unescapedId is put in last place.
But on other systems, the export order is determined by the getters' order and unescapedId is put in 1st place, which leads to comparison errors in the unit tests.

What is the new behavior (if this is a feature change)?
To prevent this discrepancy, the order is manually fixed.

Does this PR introduce a breaking change or deprecate an API?

• Yes
• No

If yes, please check if the following requirements are fulfilled

• The Breaking Change or Deprecated label has been added
• The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

Other information:

This problem was spotted via the pypowsybl "Snapshot CI" action. The problem occurs for the following jobs:

• Build windows cp310 wheel
• Build windows cp312 wheel

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud