Make User::email required

It shouldn't be required, but it's necessary for Carbon::Emailable.

db/migrations/00000000000001_create_users.cr

@@ -5,7 +5,7 @@ class CreateUsers::V00000000000001 < Avram::Migrator::Migration::V1
 
       add name : String, unique: true
       add encrypted_password : String # NOTE: Should really be called 'password_hash'
-      add email : String?, unique: true
+      add email : String, unique: true # NOTE: Should be nilable, but Carbon::Emailable doesn't really support it
       add created_at : Time
     end
   end

src/models/role.cr

@@ -3,6 +3,6 @@ class Role < BaseModel
     column name : String
     column description : String?
 
-    has_many users : User, foreign_key: :primary_role_id #####
+    has_many users : User, foreign_key: :primary_role_id
   end
 end

src/models/user.cr

@@ -5,7 +5,7 @@ class User < BaseModel
   table do
     column name : String
     column encrypted_password : String
-    column email : String?
+    column email : String
     column created_at : Time
 
     belongs_to primary_role : Role