KB-13903 | Replace Video file in existing resource

[SnehaAthul]

Adds two new APIs to ExtendedContentController:

• POST /content/v1/durationSync/:identifier — recalculates a course's total duration from scratch by summing durations across its leaf nodes (duration for Learning Resources, expectedDuration for Course Assessments), then updates it via systemUpdate.
• POST /content/v1/replaceVideo — replaces a resource's video (URL, storage keys, duration) and syncs the same fields into the resource node and the course's Cassandra hierarchy.

Changes

Duration Sync:

• Reads the course node, extracts leafNodes, and reads each leaf node individually via the Content Read API.
• Sums duration for Learning Resource nodes and expectedDuration for Course Assessment nodes.
• Updates the course's duration field via systemUpdate.

replaceVideo

• Replaces a resource's video and syncs details (previewUrl, artifactUrl, downloadUrl, cloudStorageKey, s3Key, duration) across both the resource node and the course hierarchy.
• Derives cloudStorageKey from new videoUrl; duration via ffprobe.
• Updates resource via systemUpdate, then recursively updates the matching leaf in the course's Cassandra hierarchy.

Dependencies
Requires ffprobe (part of FFmpeg) installed — used by replaceVideo to determine video duration.