Fix for PAR request failure when the PAR URL domain is different from the resident IDP/token URL

An optional configuration is introduced to configure the PAR request URI when the domain of the PAR request is different from the resident IDP URL.

In IS toml, configure the following if required,

[open_banking.identity.extensions]
push_auth_request_url = "<the par request URL should be entered here>"

Related Issue link: #204

Doc Issue: N/A

Applicable Labels: OB3, IAM Accelerator

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

Conformance Tests Details

Resources

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

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