Inconsistency in storage interfaces

[afilippov1985]

Somewhere function must return false if value not exist (ClientInterface::getClientDetails())
Somewhere function must return null in such case (AuthorizationCodeInterface::getAuthorizationCode())
Somewhere behavior not defined (PublicKeyInterface::getPrivateKey())

I suggest to revise interfaces and
return null if value not exist (not defined)
return false on error

[bshaffer]

This seems like a good idea. I seem to remember returning false for a specific reason, but it may have just been because Pdo returns false from its queries, which is not a real good reason.

[afilippov1985]

Also, existing storages has functions to set data for unit tests (such as setClientDetails, setScope, setClientKey, unsetAccessToken, setUser). They should be added to corresponding storage interfaces.

[bshaffer]

I disagree with this second request. These are convenience functions, and if you add your own storage classes, you are free to add these functions or not. The library classes require them for testing, but the actual OAuth server does not require them.