feat: setup captain limits (#10713)

This pull request introduces several changes to implement and manage
usage limits for the Captain AI service. The key changes include adding
configuration for plan limits, updating error messages, modifying
controllers and models to handle usage limits, and updating tests to
ensure the new functionality works correctly.

## Implementation Checklist

- [x] Ability to configure captain limits per check
- [x] Update response for `usage_limits` to include captain limits
- [x] Methods to increment or reset captain responses limits in the
`limits` column for the `Account` model
- [x] Check documents limit using a count query
- [x] Ensure Captain hand-off if a limit is reached
- [x] Ensure limits are enforced for Copilot Chat
- [x] Ensure limits are reset when stripe webhook comes in 
- [x] Increment usage for FAQ generation and Contact notes
- [x] Ensure documents limit is enforced

These changes ensure that the Captain AI service operates within the defined usage limits for different subscription plans, providing appropriate error messages and handling when limits are exceeded.

config/locales/en.yml

@@ -230,7 +230,8 @@ en:
       name: 'Linear'
       description: 'Create issues in Linear directly from your conversation window. Alternatively, link existing Linear issues for a more streamlined and efficient issue tracking process.'
   captain:
-    copilot_error: 'Please connect an assistant to this inbox to use copilot'
+    copilot_error: 'Please connect an assistant to this inbox to use Copilot'
+    copilot_limit: 'You are out of Copilot credits. You can buy more credits from the billing section.'
   public_portal:
     search:
       search_placeholder: Search for article by title or body...