[dy] Update oauth token column type

[dy46]

Description

This PR updates the token and refresh_token fields from sa.String(255) to sa.Text(). In some rare cases, the oauth token can be longer than 255 characters, so we need to change the column type to be able to store the entire oauth token.

How Has This Been Tested?

• Tested migrations with SQLite and PostgreSQL databases
• Tested that AzureDevOps authentication works with PostgreSQL

Checklist

• The PR is tagged with proper labels (bug, enhancement, feature, documentation)
• I have performed a self-review of my own code
• I have added unit tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

cc: @wangxiaoyou1993