Change JWT Existence time

src/Project/JWTHandler.cs

@@ -77,7 +77,7 @@ namespace Coscine.Api.Project
             var payloadClaims = payloadContents.Select(c => new Claim(c.Key, c.Value));
 
             DateTime centuryBegin = new DateTime(1970, 1, 1);
-            var exp = new TimeSpan(DateTime.Now.AddYears(1).Ticks - centuryBegin.Ticks).TotalSeconds;
+            var exp = new TimeSpan(DateTime.Now.AddMinutes(30).Ticks - centuryBegin.Ticks).TotalSeconds;
             var now = new TimeSpan(DateTime.Now.Ticks - centuryBegin.Ticks).TotalSeconds;
 
             var payload = new JwtPayload(payloadClaims);