[theztefan]

Adds validators for the vendor patterns in #43.

• Add Flickr, ClickUp, Vercel, Datadog, LaunchDarkly, PagerDuty, and BrowserStack checks.
• Add mocked tests and document the new validators and site settings.

Tests: uv run python -m pytest tests/ -q --tb=short (206 passed).

Closes #43

[Copilot]

🟢 Approval recommended

No active review issues are recorded for the new vendor validators and token aliases.

No open issues 🎉

What changed in this PR

Adds seven vendor integrations to validate secrets detected by the custom patterns in #43, with aliases for Vercel CLI and LaunchDarkly access tokens.

Changes:

• Adds read-only validation requests with conservative valid/invalid/unknown outcomes and allowlisted regional hosts.
• Introduces isolated HTTP handling that disables redirects and avoids logging credentials or response bodies.
• Adds validator, registry, and CLI coverage; replaces existing live-request tests with mocks and documents configuration.

File	Description
tests/​test_vendor_validators.py	Tests request contracts, responses, regional settings, and credential protection.
tests/​test_vendor_cli.py	Tests validator listing and CLI validation.
tests/​test_validators.py	Replaces live requests with mocks and specific assertions.
tests/​test_registry.py	Verifies new validator names and metadata.
src/​validate_secrets/​validators/​vercel_cli_token.py	Reuses Vercel validation for CLI tokens.
src/​validate_secrets/​validators/​vercel_access_token.py	Validates Vercel tokens through the user endpoint.
src/​validate_secrets/​validators/​pagerduty_api_key.py	Checks PagerDuty abilities in one configured region.
src/​validate_secrets/​validators/​launchdarkly_api_key.py	Checks LaunchDarkly API-token identity on an allowed host.
src/​validate_secrets/​validators/​launchdarkly_access_token.py	Adds the LaunchDarkly access-token alias.
src/​validate_secrets/​validators/​flickr_api_key.py	Checks Flickr keys using form POST and documented error handling.
src/​validate_secrets/​validators/​datadog_api_key.py	Validates Datadog keys against one configured site.
src/​validate_secrets/​validators/​clickup_api_key.py	Checks ClickUp keys through the authorized-user endpoint.
src/​validate_secrets/​validators/​browserstack_token_url.py	Parses credentials and checks BrowserStack Automate access.
src/​validate_secrets/​validators/​_http.py	Provides isolated requests, input checks, and credential-safe logging.
README.md	Documents new validators, regional settings, and limitations.
docs/​development.md	Updates offline testing guidance.

_{Review effort: Balanced}