RBAC assignment methods

[aarongodin]

Addresses one component of https://github.com/grafana/identity-access-team/issues/424

This adds a set of methods on the client for interacting with the RBAC assignment through the /api/access-control/:resource endpoints.

One noteworthy change is that, to make all resources share the same logic for calling the API, I added an abstraction in resource_permissions.go. The methods in service_account_permissions.go were the only ones interacting with the desired endpoints. As such, I felt it was acceptable to make a breaking change by deleting the methods in that file and replacing them with ones that follow the same naming scheme as the other resources.

Additionally, I made all methods accept either an id or a uid through an interface called ResourceIdent. Since our endpoints allow for both, it seems best to have a generic way to pass these values as they can be either int64 or string.

[CLAassistant]

All committers have signed the CLA.

[aarongodin]

I added testify to the go.mod in the project and it seems to have broke the golangci-lint command.

[IevaVasiljeva]

Nice work! I've left a few minor comments, but I think it's also good to merge as is after the imports are sorted out.

Regarding dependency management - I wonder if we need to update Go version 🤔 1.14 seems pretty old, and I think I've had similar issues in the past and bumping up the version helped.

I think it's fine to change the code of service_account_permissions.go, I don't think it would have been widely used. But we do need to make sure to change the service account permission resource of Terraform accordingly. We should also add deprecation notices to the current permission endpoints for folders etc (but that can be done in another PR).

[IevaVasiljeva]

Thanks for all the responses! All looks good to me, so I'd be happy with this being merged now. What do you think?