[OB3] Provide config for making transport cert optional for the token endpoint

[aka4rKO]

[OB3] Provide config for making transport cert optional for the token endpoint

This PR contains an improvement to the accelerator to stop mandating the transport certificate for the token request. The transport certificate is mandated to bind the certificate to the access token using the "cnf" claim.

However to properly omit sending the transport the following configs also need to be added and must remove the MTLSEnforcementValidator like below:

#[[open_banking.identity.token_filter_validators]]
#class = "com.wso2.openbanking.accelerator.identity.token.validators.MTLSEnforcementValidator"

[[open_banking.identity.token_filter_validators]]
class = "com.wso2.openbanking.accelerator.identity.token.validators.MTLSCertificateValidator"

[[open_banking.identity.token_filter_validators]]
class = "com.wso2.openbanking.accelerator.identity.token.validators.SignatureAlgorithmEnforcementValidator"

[[open_banking.identity.token_filter_validators]]
class = "com.wso2.openbanking.accelerator.identity.token.validators.ClientAuthenticatorValidator"

Issue link: https://github.com/wso2-enterprise/wso2-ob-internal/issues/871

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Development Checklist

1. Built complete solution with pull request in place.
2. Ran checkstyle plugin with pull request in place.
3. Ran Findbugs plugin with pull request in place.
4. Ran FindSecurityBugs plugin and verified report.
5. Formatted code according to WSO2 code style.
6. Have you verify the PR does't commit any keys, passwords, tokens, usernames, or other secrets?
7. Migration scripts written (if applicable).
8. Have you followed secure coding standards in WSO2 Secure Engineering Guidelines?

Testing Checklist

1. Written unit tests.
2. Documented test scenarios(link available in guides).
3. Written automation tests (link available in guides).
4. Verified tests in multiple database environments (if applicable).
5. Verified tests in multiple deployed specifications (if applicable).
6. Tested with OBBI enabled (if applicable).
7. Tested with specification regulatory conformance suites (if applicable).

Automation Test Details

Test Suite	Test Script IDs
Integration Suite	TCXXXXX, TCXXXX

Conformance Tests Details

Test Suite Name	Test Suite Version	Scenarios	Result
Security Suite	VX.X	Foo, Bar	Passed

Resources

Knowledge Base: https://sites.google.com/wso2.com/open-banking/

Guides: https://sites.google.com/wso2.com/open-banking/developer-guides