Check CSRF token in UsageData API - RUN AS-IF-FOSS

What does this MR do?

• Add CSRF check for UsageData API
• Add a note in docs
• Add test

Derived from discussions:

1. !41301 (comment 408643317)
2. !41301 (comment 408757391)
3. !41301 (comment 408757389)
4. !41301 (comment 410005328)

Example before CSFR check

curl --request POST -H "Authorization: Bearer hkXN5s5iz-kNisaqSpzk" "http://localhost:3000/api/v4/usage_data/increment_unique_users"  -D "name=g_analytics_insights" 

Example with CSFR check

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #247454 (closed)