Optional observation data should not be required

[BenjaminPelletier]

report.json is not attached because
Not needed; checks are specifically identified below.

Test check
Current state present and Altitude is present

Difference from expected behavior
While ASTM F3411 requires many fields to be transmitted between Service Provider and Display Provider, it is intentionally flexible regarding information transmitted between Display Provider and Display Application -- specifically, there are requirements regarding integrity of information transfer, but no minimum data requirements for the DP-DA interface. Since the InterUSS NetRID observation interface is observing at the Display Application point, it correspondingly makes nearly all data optional. Relevant to the two checks above, current_state is optional and alt is optional. The requirement claimed to be violated is NET0470 which says "A Net-RID Display Provider shall (NET0470) provide access to required and optional fields defined in Table 1 to Remote ID Display Applications." However, Note 19 immediately below that requirement clarifies that "Remote ID Display Applications are not required to request or display every required field defined in Table 1 as some may not be required by local regulations." Some DA implementations may not request or display current state or altitude, and therefore they would not populate those fields in the InterUSS observation response, but these implementations would still be compliant with NET0470 per Note 19. Therefore, when these fields are missing, the checks (and subsequent dependent checks) should be skipped rather than failed.