Cosmos-sdk: Restricted CoinKeeper

[rigelrozanski]

@gamarin2 came up with a cool idea, maybe we want to have a coinkeeper which has restricted access to certain tokens - heck while we're at it may be cool to have restricted accounts too..... not to mention explicit separation of read vs. read/write functionality

[gamarin2]

Yep some mapper's function are more sensitive than others. It would be cool that module devs create "modes" for their mappers with more or less capabilities for each mode.

If a module requires access to another module's mapper, app developer will be able to only pass an instance of said mapper that makes sense for the module. For example gov module needs access to a read/write instance of bank module's mapper, but for Atom only. It also needs access to staking module's mapper, but read-only.

[ebuchman]

Least-privilege for the win! https://en.wikipedia.org/wiki/Principle_of_least_privilege

[tarcieri]

It would be cool that module devs create "modes" for their mappers with more or less capabilities for each mode.

It's beginning to sound a lot like objcap...

[cwgoes]

Closed in favor of https://github.com/cosmos/cosmos-sdk/issues/802.