feat(api): add provider available

[pedrooot]

Description

Track whether a provider account still exists, for ephemeral accounts that may be deleted.

• Add available boolean field to Provider (root level, default True)
• Read-only for users (not editable via PATCH), filterable via ?filter[available]=true|false
• Custom ProviderNotAvailableError exception with check_available() model method
• Unavailable providers return HTTP 400 on:
  • Connection checks (POST /providers/{id}/connection)
  • Scan creation (POST /scans)
  • Schedule creation (POST /schedules/daily)
• Defense in depth: connection tasks and scans also skip internally if available=False

Steps to review

Please add a detailed description of how to review this PR.

Checklist

Community Checklist

• This feature/issue is listed in here or roadmap.prowler.com
• Is it assigned to me, if not, request it via the issue/feature in here or Prowler Community Slack

• Review if the code is being covered by tests.
• Review if code is being documented following this specification https://github.com/google/styleguide/blob/gh-pages/pyguide.md#38-comments-and-docstrings
• Review if backport is needed.
• Review if is needed to change the Readme.md
• Ensure new entries are added to CHANGELOG.md, if applicable.

SDK/CLI

• Are there new checks included in this PR? Yes / No
  • If so, do we need to update permissions for the provider? Please review this carefully.

UI

• All issue/task requirements work as expected on the UI
• Screenshots/Video of the functionality flow (if applicable) - Mobile (X < 640px)
• Screenshots/Video of the functionality flow (if applicable) - Table (640px > X < 1024px)
• Screenshots/Video of the functionality flow (if applicable) - Desktop (X > 1024px)
• Ensure new entries are added to CHANGELOG.md, if applicable.

API

• All issue/task requirements work as expected on the API
• Endpoint response output (if applicable)
• EXPLAIN ANALYZE output for new/modified queries or indexes (if applicable)
• Performance test results (if applicable)
• Any other relevant evidence of the implementation (if applicable)
• Verify if API specs need to be regenerated.
• Check if version updates are required (e.g., specs, Poetry, etc.).
• Ensure new entries are added to CHANGELOG.md, if applicable.

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[github-actions]

✅ Conflict Markers Resolved

All conflict markers have been successfully resolved in this pull request.

[github-actions]

✅ All necessary CHANGELOG.md files have been updated.

[jfagoagas]

I'm not sure about the naming and the location of this new field. Even though we need the provider status I'm a little bit confused. If we want to be able to enable/disable we can create a new enabled field. On the contrary since this is being created looking for a future Organizations integration maybe another table can solve it where we can store the status between the account and their parent organization.

Is this a replacement of connection.connected? If so we can mark the field as deprecated.

Thoughts? @Alan-TheGentleman @alejandrobailo @AdriiiPRodri @josemazo @vicferpoy