feat(reverse-proxy): implement user blacklist functionality

[deshmukhmayur]

Explain the feature/fix

Added a user blacklist feature to the reverse proxy service, allowing the service to block requests from specified users based on identifiers such as uid, email, or rhatUUID. This includes the addition of a new environment variable BLACKLIST_FILE_PATH to specify the path to the blacklist file, which is loaded at startup. Updated middleware to check against the blacklist and return a 403 status for blocked users. Documentation in README.md has been updated to reflect these changes, and example blacklist file provided.

• Introduced blacklistBearer and blacklistOidc middleware for handling blacklist checks.
• Created utility functions for loading and parsing the blacklist file.
• Added tests for the new functionality to ensure proper behavior.

Assisted-By: Cursor cursoragent@cursor.com

Does this PR introduce a breaking change

No.

Screenshots

N/A

Ready-for-merge Checklist

• Expected files: all files in this pull request are related to one feature request or issue (no stragglers)?
• Does the change have appropriate unit tests?
• Did tests pass?
• Did you update or add any necessary documentation (README.md, WHY.md, etc.)?
• Was this feature demoed and the design review approved?

[yashoswalyo]

LGTM