* Add a helper for mocking a provider with a state store
* Update tests to use the new helper
* Update other test fixtures for consistency
The related tests pass before and after this change
* Update testing helper to return the underlying type, not the interface
* Store the FQN of the provider used in PSS in representations of the parsed config.
This can only be done once modules have been parsed and the required providers data is available. There are multiple places where config is parsed, into either Config or Module structs, so this needs to be implemented in multiple places.
* Update affected tests, improve error diagnostic
* Begin enabling method to return a backend.Backend made using state_store config.
State store config can now be received via BackendOpts and there is rough validation of whether the config makes sense (does the provider offer a store with the given name?).
* Update code's logic to include possibility of a state store being in use
At this point there are no cases that actually handle the state store scenarios though!
* Add empty cases for handle all broad init scenarios involving PSS
* Update default case's error to report state store variables
* Improve how we resolve the builtin terraform provider's address
* Add test that hits the code path for adding a state store to a new (or implied local) project
* Add test for use of `-reconfigure` flag; show that it hits the code path for adding a state store for the first time
* Add test that hits the code path for removing use of a state store, migrating to (implied) local backend
* Add test that hits the code path for changing a state store's configuration
* Update existing test names to be backend-specific
* Add tests that hits the code path for migrating between PSS and backends
* Consolidate PSS-related tests at end of the file
* Fix log text
* Add test showing that using variables is disallowed with state_store and nested provider blocks
* Update test name
* Fix test cases
* Add TODOs so we remember to remove experiments from tests
* Update state store-related tests to use t.Cleanup
* Remove use of `testChdir`
