Support Bulk Importing Contacts via Mailtrap API

[yanchuk]

Overview

Add support to the SDK for importing Contacts in bulk via the Mailtrap API, following the official API documentation and OpenAPI specification (see below).

References

• Mailtrap API Docs - Import Contacts
• Import contacts in bulk with support for custom fields and list management. Existing contacts with matching email addresses will be updated automatically. You can import up to 50,000 contacts per request. The import process runs asynchronously - use the returned import ID to check the status and results.

Requirements

• Implement client methods for the import contacts endpoint, supporting file upload and all API parameters.
• Ensure full request/response models are covered per API docs and OpenAPI spec.
• Add input validation and error handling for all API responses (401, 403, 404, 415, 422, 429, 500).
• Provide usage examples and documentation for import contacts functionality.

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Please reach out in this issue if clarification is needed on API behavior or edge cases.