OAuth2 issuer resolution should be applied only for sub organizations

[HasiniSama]

Description

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This is an internal bug fix where the OAuth2 issuer resolution is called for parent organisations when the sub organisation depth is >1.

Steps to Reproduce

N/A

Version

7.3.0

Environment Details (with versions)

No response

Developer Checklist

• [Behavioural Change] Does this change introduce a behavioral change to the product?
•  ↳ Approved by team lead
•  ↳ Label impact/behavioral-change added
• [Migration Impact] Does this change have a migration impact?
•  ↳ Migration label added (e.g., 7.2.0-migration)
•  ↳ Migration issues created and linked
• [New Configuration] Does this change introduce a new configuration?
•  ↳ Label config added
•  ↳ Configuration is properly documented

[HasiniSama]

PRs:

• Limit OAuth2 issuer resolution only for sub organizations wso2-extensions/identity-inbound-auth-oauth#3145