export_discoveries crash

[marcorosa]

In some cases, the export_discoveries will crash the UI

Issue experienced when using docker and postgres db. This happens when exporting discoveries of large repos (e.g., credential digger's repo itself that has 7k+ discoveries).

The UI will lag for some time, and then crash. From the loggers it's visible the following message:

credential_digger_backend | psycopg2.errors.StatementTooComplex: stack depth limit exceeded   
credential_digger_backend | HINT:  Increase the configuration parameter "max_stack_depth" (currently 2048kB), 
                                                  after ensuring the platform's stack depth limit is adequate.
credential_digger_backend | 
credential_digger_backend | ERROR:backend.client_ui:There was an ERROR. rollbackthe db and restart. 
credential_digger_backend | ERROR:backend.client_ui:current transaction is aborted, commands ignored until end of transaction block