Lock should be a properly interned string
By using a concatination of an interned string with another string, the resulting string will not be interned itself - making for non-functional lock.
OF-1336: Introduce UserPropertyProvider
This commit adds a new feature to Openfire, that allows one to store user properties in an external system. This is quite similar to concepts like UserProvider, AuthProvider, GroupProvider, and so on.
The default behavior, moved from the User class to DefaultUserPropertyProvider, continues to use the ofUserProp database table. Provider implementations matching those of other types of providers have been added.
