fix(github): made token expiration fields nullable

[ysinghc]

Summary

What does this PR do?

This PR fixes a MySQL datetime error that occurs when creating GitHub connections with Personal Access Tokens (PATs). The fix modifies the token_expires_at and refresh_token_expires_at columns in the _tool_github_connections table to be nullable.

The Problem:

• MySQL rejects '0000-00-00' datetime values with error: Error 1292 (22007): Incorrect datetime value: '0000-00-00' for column 'token_expires_at'
• PAT-based GitHub connections don't have OAuth-style token expiration, so these fields should be NULL
• The database columns were not nullable, causing connection creation to fail

The Solution:

• Added a database migration script to alter token_expires_at and refresh_token_expires_at columns to be nullable (*time.Time)
• This allows PAT connections to store NULL values while OAuth connections can still store actual expiration timestamps

Does this close any open issues?

Closes #8693

Screenshots

Other Information

[Copilot]

Pull request overview

This PR fixes a MySQL datetime error that occurs when creating GitHub connections with Personal Access Tokens (PATs). The issue arose because MySQL rejects '0000-00-00' datetime values, which were being used for PAT connections that don't have OAuth-style token expiration. The fix makes the token_expires_at and refresh_token_expires_at columns nullable, allowing PAT connections to store NULL values while OAuth connections can still store actual expiration timestamps.

Changes:

• Modified TokenExpiresAt and RefreshTokenExpiresAt fields from time.Time to *time.Time in the GithubConnection model
• Added nil check in token refresh logic to prevent attempting token refresh for PAT connections
• Updated all test files to use pointer values for token expiration timestamps
• Created database migration to alter columns to be nullable

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
backend/plugins/github/models/connection.go	Changed TokenExpiresAt and RefreshTokenExpiresAt fields to pointers (*time.Time) and updated UpdateToken signature
backend/plugins/github/models/migrationscripts/20260211_modify_connection_token_expires_at_to_nullable.go	Added new migration script to make token expiration fields nullable in database
backend/plugins/github/models/migrationscripts/register.go	Registered the new migration script
backend/plugins/github/token/token_provider.go	Added nil check for TokenExpiresAt before dereferencing, and updated to pass pointers to UpdateToken
backend/plugins/github/token/token_provider_test.go	Updated tests to create expiry time variables and pass pointers
backend/plugins/github/token/round_tripper_test.go	Updated test to create expiry time variable and pass pointer

Comments suppressed due to low confidence (1)

backend/plugins/github/token/token_provider_test.go:75

• The test cases in this file don't include a scenario where TokenExpiresAt is nil, which represents a PAT (Personal Access Token) connection without OAuth-style token expiration. Consider adding a test case like:

// Nil TokenExpiresAt (PAT token without expiration)
tp.conn.TokenExpiresAt = nil
assert.False(t, tp.needsRefresh())

This would ensure the nil check in token_provider.go (line 87-89) works correctly for PAT connections.

func TestNeedsRefresh(t *testing.T) {
	tp := &TokenProvider{
		conn: &models.GithubConnection{
			GithubConn: models.GithubConn{
				RefreshToken: "refresh_token",
			},
		},
	}

	// Not expired, outside buffer
	expiry1 := time.Now().Add(10 * time.Minute)
	tp.conn.TokenExpiresAt = &expiry1
	assert.False(t, tp.needsRefresh())

	// Inside buffer
	expiry2 := time.Now().Add(1 * time.Minute)
	tp.conn.TokenExpiresAt = &expiry2
	assert.True(t, tp.needsRefresh())

	// Expired
	expiry3 := time.Now().Add(-1 * time.Minute)
	tp.conn.TokenExpiresAt = &expiry3
	assert.True(t, tp.needsRefresh())

	// No refresh token
	tp.conn.RefreshToken = ""
	assert.False(t, tp.needsRefresh())
}

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[klesh]

LGTM! Good work.