initial data model implementation

app/models/user.rb

@@ -0,0 +1,27 @@
+class User < ApplicationRecord
+  has_secure_password
+
+  belongs_to :invited_by, class_name: "User", optional: true
+  has_many :invited_users, class_name: "User", foreign_key: :invited_by_id, dependent: :nullify
+
+  has_many :created_entries, class_name: "Entry", foreign_key: :created_by_id, dependent: :nullify
+  has_many :updated_entries, class_name: "Entry", foreign_key: :updated_by_id, dependent: :nullify
+  has_many :submitted_suggested_meanings,
+           class_name: "SuggestedMeaning",
+           foreign_key: :submitted_by_id,
+           dependent: :nullify
+  has_many :reviewed_suggested_meanings,
+           class_name: "SuggestedMeaning",
+           foreign_key: :reviewed_by_id,
+           dependent: :nullify
+  has_many :entry_versions, dependent: :nullify
+  has_many :comments, dependent: :nullify
+
+  enum role: {
+    contributor: 0,
+    reviewer: 1,
+    admin: 2
+  }
+
+  validates :email, presence: true, uniqueness: true
+end