M7d server - DASH Streaming API

[dsilhavy]

Feature description
Define an interface that implements the API calls for the DASH streaming API . Note that this interface will be implemented by specific adapters for the supported media players.

Relevant specifications and corresponding sections
26.501 - 5G Media Streaming (5GMS); General description and architecture (Release 17)
26.512 - 5G Media Streaming (5GMS); Protocols (Release 17)

Additional context
The interface only defines the required methods but does not do any integration with a player itself. Instead it serves as input for player specific adapters.