Add basic BetaProgram feature.

services/web/app/coffee/Features/BetaProgram/BetaProgramHandler.coffee

@@ -0,0 +1,18 @@
+User = require("../../models/User").User
+logger = require 'logger-sharelatex'
+metrics = require("../../infrastructure/Metrics")
+
+module.exports = BetaProgramHandler =
+
+	optIn: (user_id, callback=(err)->) ->
+		User.findById user_id, (err, user) ->
+			if err
+				logger.err {err, user_id}, "problem adding user to beta"
+				return callback(err)
+			metrics.inc "beta-program.opt-in"
+			user.betaProgram = true
+			user.save (err) ->
+				if err
+					logger.err {err, user_id}, "problem adding user to beta"
+					return callback(err)
+				return callback(null)