feat: Add three new DPoP errors to CredentialsManagerException

[pmathew92]

Changes

Added 3 new error type to the CredentialsManagerException class when DPoP is used:

• DPOP_KEY_MISSING : Thrown when the stored credentials are Dpop bound but the key-pair is no longer available in KeyStore
• DPOP_NOT_CONFIGURED : Thrown when credentials are Dpop bound but the AuthenticationAPIClient used by the CredentialsManager was not configured to use DpoP
• DPOP_KEY_MISMATCH : Thrown when the key pair used while creating the token and refresh token is different from the key pair used while trying to refresh the token.

Testing

Please describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. Since this library has unit testing, tests should be added for new functionality and existing tests should complete without errors.

• This change adds unit test coverage

• This change adds integration test coverage

• This change has been tested on the latest version of the platform/language or why not

Checklist

• I have read the Auth0 general contribution guidelines

• I have read the Auth0 Code of Conduct

• All existing and new tests complete without errors