add new identifier for unknown character

[EtienneLt]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [x] 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? feature

What is the new behavior (if this is a feature change)? it adds a new identifier to identify some network elements which has one or more unknown character in his id

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

• [ ] Yes
• [x] No

[EtienneLt]

forgot a test for serialization/deserialization

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.2% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud