Jira Server/Data Center authentication with token not working

[julienfoenet]

With my team, we are testing the integration with Jira and the indexing of Jira issues from a specific Jira project. We have Jira hosted on our own (Jira Data Center, not Jira Cloud). Cloud Jira requires to authenticate using an email + password, while self-hosted Jira requires only a Personal Access Token. When we try to create the connector and indexing using our token, we see an error 401 Unauthorized, it seems that the wrong authentication method is used connect to Jira API.
This is due to the fact that in the connector code when we load the credentials, we populate the creds dict with two keys "jira_user_email" and "jira_api_token", and right after in method build_jira_client, we do a switch on the presence of the key "jira_user_email" (which is always there) to decide what authent method to use.
I think the switch should be made instead on whether user_email is provided by the user or not.

PR link:
#3852