Runs a credentials prompt for the this.
The actual prompter implementation receives the prompt through ECredentialsPrompterImplClass:
ECredentialsPrompterImpl:process_prompt(), where the given prompt_id is used for an identification. The prompt is
left 'active' as long as it is not finished with a call of
prompt_finish. This should be called even for cancelled prompts. The prompt can be cancelled before it's processed, using the
cancel_prompt.
The auth_source can be the same as cred_source, in case the credentials are stored only for that particular
source. If the sources share credentials, which can be a case when the auth_source is part of a collection, then the
cred_stource can be that collection source.
| this | |
| prompt_id |
a prompt ID to be passed to prompt_finish |
| auth_source |
an Source, to prompt the credentials for (the source which asked for credentials) |
| cred_source |
a parent Source, from which credentials were taken, or should be stored to |
| error_text |
an optional error text from the previous credentials prompt; can be null |
| credentials |
credentials, as saved in keyring; can be empty, but not null |