[SDL 0298] Processing of unknown enum values by SDL Core

[theresalech]

Proposal: Processing of unknown enum values by SDL Core

The main purpose of this proposal is to gracefully handle unknown enum values from a mobile RPC request with any given SDL Core version. This can be achieved by improving the way SDL Core processes and validates unknown enum values.

Review: smartdevicelink/sdl_evolution#989

Steering Committee Decision:

The Steering Committee voted to accept this proposal with the following revision: update the example in the Motivation section to use a mobile application and SDL Core instance using future versions of their respective SDL libraries, instead of 5.0 and 4.3.
The proposal .md file was updated to reflect these revisions on 5/21/2020.

[jacobkeeler]

Closing with the merge of #3385