chore: do not refresh tokens that have already failed refreshing (#15608)

Once a token refresh fails, we remove the `oauth_refresh_token` from the
database. This will prevent the token from hitting the IDP for
subsequent refresh attempts.

Without this change, a bad script can cause a failing token to hit a
remote IDP repeatedly with each `git` operation. With this change, after
the first hit, subsequent hits will fail locally, and never contact the
IDP.

The solution in both cases is to authenticate the external auth link. So
the resolution is the same as before.

coderd/database/dbmem/dbmem.go

@@ -8512,6 +8512,29 @@ func (q *FakeQuerier) RegisterWorkspaceProxy(_ context.Context, arg database.Reg
 	return database.WorkspaceProxy{}, sql.ErrNoRows
 }
 
+func (q *FakeQuerier) RemoveRefreshToken(_ context.Context, arg database.RemoveRefreshTokenParams) error {
+	if err := validateDatabaseType(arg); err != nil {
+		return err
+	}
+
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+	for index, gitAuthLink := range q.externalAuthLinks {
+		if gitAuthLink.ProviderID != arg.ProviderID {
+			continue
+		}
+		if gitAuthLink.UserID != arg.UserID {
+			continue
+		}
+		gitAuthLink.UpdatedAt = arg.UpdatedAt
+		gitAuthLink.OAuthRefreshToken = ""
+		q.externalAuthLinks[index] = gitAuthLink
+
+		return nil
+	}
+	return sql.ErrNoRows
+}
+
 func (q *FakeQuerier) RemoveUserFromAllGroups(_ context.Context, userID uuid.UUID) error {
 	q.mutex.Lock()
 	defer q.mutex.Unlock()