How to authenticate with basic_auth having a '/' in it's username


I intend to use tyk-gateway-ce on some pre-existing webservices.
For legacy reasons, some of my users have the ‘/’ character in their basicAuth username and I’d like them to keep using the same credentials.
Thus, I want to create an apiKey with a ‘/’ in it’s name, which is a problem obviously as the key username is part of the url.

For example : calling http://myTykHost/tyk/keys/John/Doe with a valid key body, hoping to create a key for ‘John/Doe’, only returns a 404.
Same thing with an escaped character or pre-encoded (%2F) character

I know allowing special characters in our users login is not great, but I can’t change that now.
How would you approach the problem ?

One of the options can be simple PRE middleware which rewrites / symbol inside header to another character, and when you migrate users to the Tyk, replace / symbol when creating the key as well.

Thank you for your answer,
I’ll try and implement that