temporary id's for new sources

[olhsha]

Temprary id-s for new sources can be any strings, not necessarily uuid's (at the moment the server expects only uuid's). The server should detect if the provided string is an uuid. If not then the source is definitely new and the server generates an uuid for it while adding to the database. If yes, the server checks if the source with this uuid is already in the DB.

The client may have, in its own DB, the mapping between its id's and the ones given by the server.