Refactor prepareIntrospectionResponse to use ensureType to avoid panic behaviour

[MohamedSabthar]

Description:
In the current implementation of the oauth2, the prepareIntrospectionResponse method panics in multiple places. This is primarily caused by the use of explicit casting (Diamond Operator). However, using diamond operator is not recommended as it leads to unexpected failures.

Expected Behavior:

• The current casting logic should be refactored to use the ensureType method instead.
• If an error occurs while using ensureType, the introspection response should be considered invalid and OAuth2 validation should fail due to authorization server does not follow the RFC specification.

Solution:

• Refactor all instances where diamond-operator/checkpanic is used in the prepareIntrospectionResponse method to use ensureType.
• Handle the error gracefully by marking the introspection response as invalid.

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