Handle blocked time ranges

[defagos]

As an editor I want content that must not be available (e.g. legal, commercial or geoblocking reason) not to be playable (skipped). As a user I still want to be able to play content containing blocked time ranges.

Acceptance criteria

• Content that is blocked for a reason (legal, commercial, geoblocking, etc.) cannot be played / seen.
• Content that is partially blocked can be played where not blocked.
• Nested blocked ranges are supported.

Tasks

• [x] Skip over blocked time ranges during playback.
• [x] Prevent seeks into blocked intervals early.
• [x] Prevent from starting at a blocked position.
• [x] Add manually crafted example with blocked intervals to the demo.
• [x] Parse blocked segment in IL metadata.
• [x] Set blocked time ranges as interstitials.
• [x] Check corner cases (e.g. blocked range starting at zero).

[defagos]

tvOS interstitials cannot be nested (otherwise the behavior is erratic). Possibly nested time ranges have to be flattened first.

[defagos]

There is a minor issue with some content with blocked time ranges at the very end (e.g. Ramdam urn:rts:video:13041988). In this case the progress is stuck at 1 after replaying the content.

This is due to issues with the low-level seek not completing with finished set to true, an issue already encountered in the past. For the moment it is better to consider it as a known issue and not to introduce silly workarounds for what is ultimately a corner case.