TO-291: Add notifications model

[almeidaraul]

Description

This PR is the first in TO-291. It creates a notifications table and model.

A notification has:

• A user id of the user being notified
• A notification type (an enum representing what the notification refers to)
• An optional target URL (the link the notification points to)
• A dismissed_at timestamp representing when the notification was marked as read by the user (null if it wasn't)

Resolved issues

Part of TO-291

Web service API changes

Added a migration

[Copilot]

Pull request overview

Adds a Notification model and database table for user notifications, with support for notification types, optional target URLs, and dismissal tracking.

Changes:

• New NotificationType enum with two values for artefact and environment review assignments
• New Notification SQLAlchemy model with user foreign key, notification type, target URL, and dismissed timestamp
• Alembic migration to create the notification table with an index on user_id
• Pydantic response models for the notifications API

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
backend/test_observer/data_access/models_enums.py	Adds NotificationType enum
backend/test_observer/data_access/models.py	Adds Notification model
backend/test_observer/controllers/notifications/models.py	Adds Pydantic response schemas
backend/migrations/versions/2026_03_10_1618-983168a63271_add_notifications.py	Alembic migration for notification table

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[Copilot]

Pull request overview

Adds a Notification model and corresponding database migration for a user notification system, along with Pydantic response models for the API layer.

Changes:

• New Notification SQLAlchemy model with user foreign key, notification type enum, optional target URL, and dismissed timestamp
• New NotificationType enum with two values for artefact and environment review assignments
• Alembic migration to create the notification table

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
backend/test_observer/data_access/models_enums.py	Adds NotificationType enum
backend/test_observer/data_access/models.py	Adds Notification model
backend/test_observer/controllers/notifications/models.py	Adds Pydantic response models for notifications
backend/migrations/versions/2026_03_10_1618-983168a63271_add_notifications.py	Alembic migration to create the notification table

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