[API] Increase username max length to 64 characters

[davidjiglesias]

Wazuh version	Component
4.0.1	RBAC

Hello team,

Currently, the API request to create a new user allows for a maximum length of 20 characters to define the username, we have decided to increase this limit to 64 characters for an increased flexibility. It affects names for all RBAC related resources (username, role name, policy name and rule name).

Regards,

David J. Iglesias

Checks

wazuh/wazuh

• Unit tests without failures. Updated and/or expanded if there are new functions/methods/outputs:
  • Cluster (framework/wazuh/core/cluster/tests/ & framework/wazuh/core/cluster/dapi/tests/)
  • Core (framework/wazuh/core/tests/)
  • SDK (framework/wazuh/tests/)
  • RBAC (framework/wazuh/rbac/tests/)
  • API (api/api/tests/)
• API tavern integration tests without failures. Updated and/or expanded if needed (api/test/integration/):
  • Affected tests
  • Affected RBAC (black and white) tests
• Review of spec.yaml examples and schemas (api/api/spec/spec.yaml)
• Changelog (CHANGELOG.md)

wazuh/wazuh-documentation

• Migration from 3.X for changed endpoints (source/user-manual/api/equivalence.rst)
• Update RBAC reference with new/modified actions/resources/relationships (source/user-manual/api/rbac/reference.rst)