SSH private key auth: If username is empty, prompt user to enter it

Description

When authenticating using SSH private key (including SSH tunnel), if the user forgets to enter a username when creating the remmina profile, the user will now be prompted to enter the username. The user can then enter the username and modify the entered password if needed. Remmina will automatically save the username to the remmina profile and will optionally save the password depending on the user's preference.

Related Issue

#2905 (closed)

Motivation and Context

If a user forgets to enter a username for SSH private key auth profiles, remmina fails to authenticate but in a manner that suggests that the user entered the incorrect password. Now the user will know that the username was missing in this case.

How Has This Been Tested?

I tested with several profiles:

• SSH private key with no username
• RDP with SSH tunnel private key with no username
• SSH private key with no username or password
• RDP with SSH tunnel private key with no username or password
• SSH username/password (no changes)

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.