Feat: Add Pydantic models for report endpoints

[elisafalk]

Overview: This PR introduces new Pydantic models to standardize request and response formats for report-related API endpoints.

Changes

• Created a new file app/models/report_models.py to house the new models.
• Defined ReportRequest with token_id (string) and optional parameters (dictionary) for incoming report requests.
• Defined ReportResponse with report_id (string) and status (string) for outgoing report responses.
• These models will ensure consistent data validation and serialization across report functionalities.