doc: model server - openai and azure openai

[cwing-nvidia]

Use cases, pain points, and background
split ticket from #194

Description:
What should we do?

Design:
What files should be touched? What logic should be written?

Out of scope:
What are some items that this issue could be mistaken to cover that this issue should explicitly NOT cover?

Acceptance Criteria:

• Individual items that need to be finished in order for this issue to be considered completed