Product/202 user invitation

coscine/issues#202

src/Migrations/Migrations/Migration202104281216InvitationTabel.cs

+using FluentMigrator;
+
+namespace Coscine.Migrations.Migrations
+{
+    //yyyymmddhhmm
+    [Migration(202104281216)]
+    public class Migration202104281216InvitationTabel : FluentMigrator.Migration
+    {
+        public override void Down()
+        {
+            Delete.Table("Invitations");
+        }
+
+        public override void Up()
+        {
+            Create.Table("Invitations")
+                .WithColumn("Id").AsGuid().NotNullable().PrimaryKey().WithDefault(SystemMethods.NewGuid)
+                .WithColumn("Project").AsGuid().NotNullable()
+                .WithColumn("Issuer").AsGuid().NotNullable()
+                .WithColumn("Role").AsGuid().NotNullable()
+                .WithColumn("InviteeEmail").AsString(200).NotNullable()
+                .WithColumn("Expiration").AsDateTime().NotNullable()
+                .WithColumn("Token").AsGuid().NotNullable().WithDefault(SystemMethods.NewGuid);
+
+            Create.ForeignKey()
+                .FromTable("Invitations").ForeignColumn("Project")
+                .ToTable("Projects").PrimaryColumn("Id");
+
+            Create.ForeignKey()
+                .FromTable("Invitations").ForeignColumn("Issuer")
+                .ToTable("Users").PrimaryColumn("Id");
+
+            Create.ForeignKey()
+                .FromTable("Invitations").ForeignColumn("Role")
+                .ToTable("Roles").PrimaryColumn("Id");
+        }
+    }
+}