Exception when [Parse setApplicationId:clientKey:] is called twice

[wzs]

Recently I've found in our codebase that +[Parse setApplicationId:clientKey:] was called twice during app initialization (with same params).

It was obviously mistake, but by the way I've found that in that case SDK throws exceptions, ie:
during call to -[PFCommandURLRequestConstructor _URLRequestHeadersForCommand], dataSource became nil (it's a weak reference to ParseManager).

It'd be nice to have an assertion preventing from changing applicationId/clientKey after it's set already or cancel all ongoing operations started from the old instance of ParseManager.

[nlutsenko]

Hey @wzs, thanks for report.
Setting applicationId and clientKey more than once is definitely not supported use case, let me put this as an enhancement and add assertion there.

PFCommandURLRequestConstructor use case is super interesting though - we should do something smarter there.

[nlutsenko]

Implemented in #874

[parse-github-assistant]

The label type:feature cannot be used in combination with type:improvement.