OAuth2 token can be used in basic auth

[techknowlogick]

This includes API calls and git clones
(username is token and password is either empty or x-oauth-basic)

@jonasfranz If possible could you review as you have most knowledge of OAuth2 implementation.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@199faad). Click here to learn what that means.
The diff coverage is 19.04%.

@@            Coverage Diff            @@
##             master    #6747   +/-   ##
=========================================
  Coverage          ?   41.02%           
=========================================
  Files             ?      421           
  Lines             ?    57955           
  Branches          ?        0           
=========================================
  Hits              ?    23777           
  Misses            ?    31022           
  Partials          ?     3156

Impacted Files	Coverage Δ
routers/repo/http.go	38.07% <11.11%> (ø)
modules/auth/auth.go	49.23% <25%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 199faad...11fc783. Read the comment docs.

[Tchoupinax]

Hello :)

This fix solves my problem ! (After migrating Gitea to 1.8 and Drone to 1.1.0). Thank you ! ;)