Go Support of Indexer v2 [5]

[EvanJRichard]

• [x] implementation plan informed by oapi design
• [x] update algod rest client
• [x] write indexer rest client
• [x] write tests: positive tests that hit all end points and negative tests that exercise listed errors (longest part, removes duplicate work for other sdks) -- [X] feature files -- [x] step impls -- [ ] mock jsondata
• [x] write handlers, update models
• [x] cleanup and docs
• [ ] review design with team and address comments

N.B. this ticket scope does not include integration tests, just unit tests.

[EvanJRichard]

note for future retrospectives/sprint planning, this ended up being significantly larger than the estimated 5 points as you can see from the log