feat: add mfa indexes

[J0]

What kind of change does this PR introduce?

Introduces indexes for mfa to target the following queries:

func FindFactorsByUser(tx *storage.Connection, user *User) ([]*Factor, error) {
 	factors := []*Factor{}
 	if err := tx.Q().Where("user_id = ?", user.ID).Order("created_at asc").All(&factors); err != nil {
 		if errors.Cause(err) == sql.ErrNoRows {
 			return factors, nil
 		}
 		return nil, errors.Wrap(err, "Database error when finding MFA factors associated to user")
 	}
 	return factors, nil
 }

Find Token by Session

func FindTokenBySessionID(tx *storage.Connection, sessionId *uuid.UUID) (*RefreshToken, error) {
 	refreshToken := &RefreshToken{}
 	err := tx.Q().Where("session_id = ?", sessionId).Order("created_at asc").First(refreshToken)
 	if err != nil {
 		if errors.Cause(err) == sql.ErrNoRows {
 			return nil, RefreshTokenNotFoundError{}
 		}
 		return nil, err
 	}
 	return refreshToken, nil
 }

https://github.com/supabase/gotrue/pull/736/files#diff-391a5058b1ace3b7d41e48d0c23859a417795c034274ae3cd5fdf2c4ad6dc7b4R104
Source: https://github.com/supabase/gotrue/pull/736/files#diff-21513bee858a7f7f89598f574f70bcac74a98ddbef23b75201960823301398d0R85

 func FindSessionByUserID(tx *storage.Connection, userId uuid.UUID) (*Session, error) {
 	session := &Session{}
 	if err := tx.Eager().Q().Where("user_id = ?", userId).Order("created_at asc").First(session); err != nil {
 		if errors.Cause(err) == sql.ErrNoRows {
 			return nil, SessionNotFoundError{}
 		}
 		return nil, errors.Wrap(err, "error finding session")
 	}
 	return session, nil
 }

https://github.com/supabase/gotrue/pull/736/files#diff-b4f2ed95a2f612a5c133f50ebc2ee346ccb1cabb36343da567c3a1e336668e94R104

The change will go into the mfa branch and we will then cherry pick the changes for merge into master

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Sanity checks: