User search does not show relevant results for complex user names.

[ksetdekov]

Actual Behaviour

There's a user with a name "PG", that I'd like to assign administrative privileges in a group, but when i search his name I can not find him in search results.

Expected Behaviour

If you enter a sequence of characters that is exactly a valid user name, you should get that user name.

Steps to reproduce it

• Open a team editing dialogue.
• Search for "_PG_" and not find this name.
• Compare it with a real account tasks.hotosm.org/users/PG

Screenshots of the issue

Would you like to work on the issue?

I'd like to, but do not know where to start.
I can code Python as a data scientist, but not skilled in front-end.