constraints: remove limit of two array elements

[andrewbonney]

Adding this as a discussion point relating to #70

Removing this limit would be less painful if done prior to v1.1. It would require a docs note adding for any servers which implement multiple versions to make clear that for the RTP transport type only, more than two legs isn't supported before v1.1.

This would allow a WebSocket Sender to list many connection_uris for different interfaces. The issue of what to do with any parameters which get duplicated between 'legs' as a result remains, but this would at least remove a blocker to some future uses.

[andrewbonney]

Doing some digging in git history this may actually be a spec bug. The restrictions on array sizing were originally removed here, but this case was likely missed: e6cd9a9

[garethsb]

To be clear, that commit (at v1.0_receiver_transport_params_rtp.json line 170) removed "maxItems": 2 (and there's the same change for senders), but it didn't make the same change in https://github.com/AMWA-TV/nmos-device-connection-management/blob/v1.0.x/APIs/schemas/v1.0-constraints-schema.json. Oops.

[andrewbonney]

We believe this can safely be treated as a fix which can be backported to v1.0. The individual transport types define how the array is used, and the RTP type (which is the only one used at v1.0) clearly defines how the array is used: https://github.com/AMWA-TV/nmos-device-connection-management/blob/v1.0.x/docs/4.1.%20Behaviour%20-%20RTP%20Transport%20Type.md#operation-with-smpte-2022-7