docs:Oauth_improve

[alejandroparra]

SUMMARY

Hi there!
I was trying to set up the Custom OAuth2 Configuration but found out that one very important and necessary import is missing from the documentation in order to make the sample code work without any problem.

the import missing is with the library OAuth, after several hours of searching and reading found that importing only that library doesn't work, what it works is to import the full OAuth library from flask_appbuilder.security.manager.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• [ x] Has associated issue: Documentation update for OAuth configuration apache/superset#17544
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API