Mark endpoints and storage indexes not necessary for state machine transistion

[robert-zaremba]

Is your feature request related to a problem? Please describe.

Blockchain is not a general DB, and it's use should be only optimized for state transition and trust operations (modules, smart-contract).
However, due to lack of good off-chain indexers, some secondary on-chain indexes were added to different modules (eg group module) only for dapp purposes.

Ref: #154 (comment)

Describe the solution you'd like

• use (mark) alpha version for RPC which relay on redundant data indexes.

The versioning schema allows us to make breaking changes. Specifically, marking an RPC as alpha means that it's not stable and may change. Hence, it shouldn't be used as a dependency of a stable or beta feature.

Describe alternatives you've considered

Alternative is to remove this endpoints, but so far we don't have a reliable solution for delivering that data off-chain.