Add new detector for Twitch OAuth Access Tokens

[juliacwiek]

Description:

This PR is being submitted on behalf of Amazon (Twitch).

Adding a new detector to identify Twitch OAuth User/App Access Tokens. The existing Twitch detector only validates Twitch OAuth Client Credentials. See below for comparison.

Twitch OAuth Client Credentials (existing detector):

• Identifies two 30-character alphanumeric strings, client_id and client_secret
• Both strings are validated together via a POST request to https://id.twitch.tv/oauth2/token
• Both strings can be used to obtain Twitch OAuth App Access Tokens
• Reference: https://dev.twitch.tv/docs/authentication/getting-tokens-oauth/ (see "Client Credentials Grant Flow")

Twitch OAuth User/App Access Tokens (new detector):

• Identifies a 30-character alphanumeric access_token string
• Validated via a GET request to https://id.twitch.tv/oauth2/validate
• Used to obtain sensitive & non-sensitive resources on the Twitch platform
• References: https://dev.twitch.tv/docs/authentication/, https://dev.twitch.tv/docs/authentication/validate-tokens/#how-to-validate-a-token

Checklist:

• Tests passing (make test-community)?
• Lint passing (make lint this requires golangci-lint)?

[CLAassistant]

All committers have signed the CLA.

[ahrav]

Thank you so much for your contribution, @juliacwiek! We really appreciate it, especially the detailed description.

[ahrav]

Thank you for updating this.

[ahrav]

Added test creds into GSM.