Update: Improve invitation handling

src/Project/Controllers/ProjectController.cs

@@ -600,7 +600,7 @@ namespace Coscine.Api.Project.Controllers
                 return Unauthorized($"You are not an owner of the project.");
             }
 
-            var invitations = _invitationModel.GetAllWhere(x => x.Project == projectId && x.Expiration > DateTime.UtcNow)
+            var invitations = _invitationModel.GetAllWhere(x => x.Project == projectId)
                 .Select(x => new InvitationReturnObject
                 {
                     Id = x.Id,
@@ -652,11 +652,22 @@ namespace Coscine.Api.Project.Controllers
                      x.Expiration > DateTime.UtcNow
             );
 
-            if (invitations != null && invitations.Any())
+            if (invitations.Any())
             {
                 return BadRequest("This invitee already has a valid invitation to this project.");
             }
 
+            var expiredInvitations = _invitationModel.GetAllWhere(
+                x => x.Project == sendInvitationObject.Project &&
+                     x.InviteeEmail == sendInvitationObject.Email &&
+                     x.Expiration <= DateTime.UtcNow
+            );
+
+            foreach (var expiredInvitation in expiredInvitations)
+            {
+                _invitationModel.Delete(expiredInvitation);
+            }
+
             var token = _invitationModel.CreateInvitation(sendInvitationObject.Project, user.Id, sendInvitationObject.Role, sendInvitationObject.Email);
 
             var body = new JObject