This refactor encapsulates key management for JWT signing and verification by:
- Introducing `ParseKeyFunc` and `SecuringKeyFn` to streamline key operations.
- Moving key-related functions to `jwt.go` to improve package modularity.
- Simplifying `Encrypt` and `Decrypt` function documentation and usage.
- Updating tests to align with the new function signatures and logic flow.

The JWT functionality has been refactored, and its associated test values are no longer required. Removing the test file helps maintain code clarity and prevents outdated test logic from impacting the current codebase.

- Renamed key functions to clarify their use.
- Removed unused `featureHeaderKey`.
- Added comprehensive tests for JWT signing and verifying.

- Streamlines key retrieval by integrating with the cryptokeys package.
- Simplifies key handling by decoding directly using hex utilities.
- Enhances validation by using context for managing key operations.
- Improves test robustness with clearer setup and consistent mocking.

- Rename package `jwt` to `jwtutils` for better context.
- Consolidate constants and enhance error messages.
- Simplify key management for JWT signing and verification.

Refactor JWT utility code to replace `ParseOptions` with more specific
`VerifyOptions` and `DecryptOptions`. This change enhances clarity and
flexibility, accommodating different needs for JWS and JWE operations. Update
tests to align with the refactored structure, ensuring robust coverage and
functionality verification.

Increase OIDC secret length for added security and clarity.
Optimize JWT test coverage with custom claims and key cache tests.

- Enhance comments for key interfaces to clarify usage
  and considerations for time validity and clock skew.
- Refactor JWE/JWS logic to simplify serialization and
  deserialization processes, ensuring more efficient and
  concise handling of JWTs. Implement compact serialization
  and remove unnecessary base64 encoding.

Removing unused test and mock code simplifies maintenance and reduces clutter.

Deleting unnecessary cryptokeys keycachemock ensures clarity and reduces maintenance.

Ensure that the dbCache methods for encrypting, decrypting, signing,
and verifying keys validate the feature flag before proceeding with
operations. This validation step prevents using keys for unintended
purposes, maintaining proper alignment with their intended
cryptographic feature.