feat: Add Gmail Catchall Labeler service with configuration and functionality

- Introduced a new Docker Compose configuration for the Gmail Catchall Labeler service.
- Implemented GmailOptions class for managing configuration settings.
- Developed GmailApiClient to interact with the Gmail API, including methods for fetching messages and managing labels.
- Created models for Gmail messages, labels, and headers.
- Added IGmailClient interface to define the contract for Gmail client implementations.
- Implemented GmailOrganizer to handle the organization of emails based on recipient addresses.
- Developed LabelNameResolver for generating label names based on local parts of email addresses.
- Created RecipientExtractor to extract local parts from email headers.
- Implemented state management with OrganizerState and StateStore for persisting state information.
- Added Worker class to manage the background processing of email organization.
- Created unit tests for GmailOrganizer, LabelNameResolver, and RecipientExtractor to ensure functionality.
- Added necessary project files and configurations for building and running the application.

.env.example

@@ -0,0 +1,3 @@
+GMAIL_CLIENT_ID=replace-with-google-oauth-client-id
+GMAIL_CLIENT_SECRET=replace-with-google-oauth-client-secret
+GMAIL_REFRESH_TOKEN=replace-with-google-oauth-refresh-token