Minor improvements to the custom authentication extension

[Thisara-Welmilla]

Description

Feature:

• Support for external custom authention extension #20809

Following minor inprovement need to be added to authentication extension feature:

1. Change user/idp to user/userIdentitySource in the request to the external service during user authentication with the custom authentication extension.
2. Improve the error messge when creating new user defined authenticators along with system defined local authenticators.
3. If the userDefined is not specified for the federated authenticator PUT request payload, the default value must be SYSTEM. Current implementation is using USER for this PUT request secnario.
4. In /v1/api/authenticators API, send the name as the federated authenticator name for the user defined authenticator.
5. Add condition for checking system authenticator which register to OSGI services at server start does not start with custom-.

Version

No response

[Thisara-Welmilla]

PRs:

• Validate system authenticators names at registering. wso2/carbon-identity-framework#6489
• Fix federated authenticator PUT request. wso2/identity-api-server#840
• Fix federated authenticator PUT request. wso2/carbon-identity-framework#6508
• Update integration test error message. #23116