How to use the sqreen.identify function in sqreen

delete ctx.state.appToken;
			delete ctx.state.tokenType;
			delete ctx.state.tokenScopes;

			// get token sent by user
			const token = retrieveToken(ctx);

			// try to authenticate with token
			const user = /[0-9a-f]{32,}/i.test(token.value) ?
				await authenticateWithAppToken(ctx, token) : // app token?
				await authenticateWithJwt(ctx, token);  // otherwise, assume it's a JWT.

			// log to sqreen
			/* istanbul ignore if */
			if (process.env.SQREEN_ENABLED) {
				require('sqreen').identify(ctx.req, { email: user.email });
			}

			// update state
			ctx.state.user = user;
			ctx.response.set('X-User-Id', user.id);

		} catch (err) {

			if (err.isApiError) {
				// update state with error if it's API-related
				ctx.state.authError = err;

			} else {
				// otherwise, re-throw (this is unexpected)
				/* istanbul ignore next */
				throw err;

// check plan config if provided
		if (_.isObject(planAttrs)) {
			for (let key in planAttrs) {
				if (planAttrs.hasOwnProperty(key)) {
					let val = planAttrs[key];
					if (user.planConfig[key] !== val) {
						throw error('User <%s> with plan "%s" tried to access `%s` but was denied access due to missing plan configuration (%s is %s instead of %s).',
							user.email, user._plan, req.url, key, val, user.planConfig[key]).display('Access denied').status(403).log();
					}
				}
			}
		}
		// *** here we're still authenticated (token is valid and not expired). ***

		if (config.vpdb.services.sqreen.enabled) {
			require('sqreen').identify(req, { email: user.email });
		}

		// this will be useful for the rest of the stack
		req.user = user;

		// set dirty header if necessary
		return redis.getAsync('dirty_user_' + user.id).then(result => {
			if (result) {
				logger.info('[ctrl|auth] User <%s> is dirty, telling him in header.', user.email);
				res.setHeader('X-User-Dirty', result);
				return redis.delAsync('dirty_user_' + user.id);
			}
			res.setHeader('X-User-Dirty', 0);
		});

	}).then(() => {