Add DB queries for account self-service

New queries: UpdateUserPassword, SoftDeleteUser, HardDeleteExpiredUsers,
CountUserOwnedTeamsWithOtherMembers, GetOAuthProvidersByUserID, DeleteOAuthProvider.

db/queries/oauth.sql

@@ -5,3 +5,9 @@ VALUES ($1, $2, $3, $4);
 -- name: GetOAuthProvider :one
 SELECT * FROM oauth_providers
 WHERE provider = $1 AND provider_id = $2;
+
+-- name: GetOAuthProvidersByUserID :many
+SELECT * FROM oauth_providers WHERE user_id = $1;
+
+-- name: DeleteOAuthProvider :exec
+DELETE FROM oauth_providers WHERE user_id = $1 AND provider = $2;