New plugin for OpenAI tokens

[Chandra158]

Please check if the PR fulfills these requirements

• Tests for the changes have been added

• Docs have been added / updated

• All CI checks are green

What kind of change does this PR introduce?

Feature: New plugin to detect OpenAI api keys

Token Format

• User API keys (legacy): sk-[20_alpha_numberic] T3BlbkFJ [20_alpha_numberic] (T3BlbkFJ = base64 for "OpenAI")
  • there's no official documentation but found this community forum which mentions legacy token format
• Project API keys: sk-<project_name>-[20_alpha_numberic] T3BlbkFJ [20_alpha_numberic]
• Generated tokens for both from OpenAI portal and verified manually

Token verification

Checking whether token is active might not be possible; so haven't implemented verify() method for the plugin:

• No official API to check validity of tokens (refs: openai api-reference)
• Calling random apis (like: v1/models) may or may not work because of the restrictions placed on tokens during creation
  • another downside could be credit usage for valid tokens

Tests

• New tests added for plugin
• Tested manually in local with sample token in file

      {
        "type": "OpenAI Token",
        "filename": "test_data/files/file_with_secrets.py",
        "hashed_secret": "007111295d396c8234d268fa24014ef5235136b0",
        "is_verified": false,
        "line_number": 5
      }