Add modality filter to ContentNode API endpoint

[rtibbles]

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Overview

Add a modality query parameter filter to the ContentNode API endpoint in kolibri/core/content/api.py to enable filtering content by modality values (COURSE, QUIZ, SURVEY, etc.).

Implementation

Since the modality field on the ContentNode model will have choices=modalities.choices, Django Rest Framework's FilterBackend should automatically infer the appropriate filter type.

Simply add "modality" to the contentnode_filter_fields list (around line 433 in kolibri/core/content/api.py):

contentnode_filter_fields = [
    "parent",
    "parent__isnull",
    # ... existing fields ...
    "modality",  # Add this
]

Usage

This will allow API calls like:

• /api/content/contentnode/?modality=COURSE - Filter to only course content
• /api/content/contentnode/?modality=QUIZ - Filter to only quiz content
• /api/content/contentnode/?modality=SURVEY - Filter to only survey content

Benefits

• Enables efficient filtering by modality without JSON field queries
• Leverages the database index on the modality field for performance
• Consistent with other simple field filters in the API

Available Modality Values

From le_utils.constants.modalities:

• COURSE
• CUSTOM_NAVIGATION
• LESSON
• QUIZ
• SURVEY
• UNIT

🤖 This issue was written by Claude Code, under supervision, review and final edits by @rtibbles 🤖