New: Add the Contact Changing functionality to the database and backend

coscine/issues#1294 coscine/issues#789

src/Migrations/Migrations/Migration202102021140ContactChange.cs

+using FluentMigrator;
+
+namespace Coscine.Migrations.Migrations
+{
+    //yyyymmddhhmm
+    [Migration(202102021140)]
+    public class Migration202102021140ContactChange : FluentMigrator.Migration
+    {
+        public override void Down()
+        {
+            Delete.Table("ContactChange");
+        }
+
+        public override void Up()
+        {
+            Create.Table("ContactChange")
+                .WithColumn("RelationId").AsGuid().PrimaryKey().WithDefault(SystemMethods.NewGuid)
+                .WithColumn("UserId").AsGuid()
+                .WithColumn("NewEmail").AsString(200).NotNullable()
+                .WithColumn("EditDate").AsDateTime().Nullable()
+                .WithColumn("ConfirmationToken").AsGuid().NotNullable().WithDefault(SystemMethods.NewGuid);
+
+            Create.ForeignKey()
+                .FromTable("ContactChange").ForeignColumn("UserId")
+                .ToTable("Users").PrimaryColumn("Id");
+        }
+    }
+}