fixed bugfix where another user could not store the same object again

fixed the primary keys => all the classes have now composite primary key which contais an id + user_id, necessary gem: 'composite_primary_keys'
fixed the user_id relation => every class now "belongs_to" user

pls kill me know

db/migrate/20200421152314_create_favorite_people.rb

@@ -1,15 +1,13 @@
 class CreateFavoritePeople < ActiveRecord::Migration[6.0]
   def change
-    create_table :favorite_people, id: false do |t|
+    create_table :favorite_people, primary_key: [:tiss_id, :user_id] do |t|
       t.integer :tiss_id, null: false
-      t.integer :user_id, null: false
+      t.belongs_to :user
       t.string :first_name
       t.string :last_name
       t.string :picture_uri
       t.string :personal_annotation
-
       t.timestamps
     end
-    add_index :favorite_people, :tiss_id, unique: true
   end
 end

db/migrate/20200521091231_create_favorite_courses.rb

@@ -1,14 +1,14 @@
 class CreateFavoriteCourses < ActiveRecord::Migration[6.0]
   def change
-    create_table :favorite_courses do |t|
+    create_table :favorite_courses , primary_key: [:id, :user_id] do |t|
+      t.integer :id
+      t.belongs_to :user
       t.string :number, null: false
       t.string :semester, null: false
       t.string :title, null: false
-      t.integer :user_id, null: false
       t.string :personal_annotation
 
       t.timestamps
     end
-    add_index :favorite_courses, [:number, :semester], unique: true
   end
 end

db/migrate/20200525132942_create_favorite_theses.rb

@@ -1,13 +1,12 @@
 class CreateFavoriteTheses < ActiveRecord::Migration[6.0]
   def change
-    create_table :favorite_theses, id: false do |t|
+    create_table :favorite_theses, primary_key: [:id, :user_id] do |t|
       t.integer :id, null: false
-      t.integer :user_id, null: false
+      t.belongs_to :user
       t.string :title
       t.string :personal_annotation
 
       t.timestamps
     end
-    add_index :favorite_theses, :id, unique: true
   end
 end

db/migrate/20200529081537_create_favorite_projects.rb

@@ -1,13 +1,12 @@
 class CreateFavoriteProjects < ActiveRecord::Migration[6.0]
   def change
-    create_table :favorite_projects, id: false do |t|
+    create_table :favorite_projects, primary_key: [:id, :user_id] do |t|
       t.integer :id, null: false
-      t.integer :user_id, null: false
+      t.belongs_to :user
       t.string :title
       t.string :personal_annotation
 
       t.timestamps
     end
-    add_index :favorite_projects, :id, unique: true
   end
 end

db/schema.rb

@@ -12,47 +12,48 @@
 
 ActiveRecord::Schema.define(version: 2020_05_29_081537) do
 
-  create_table "favorite_courses", force: :cascade do |t|
+  create_table "favorite_courses", primary_key: ["id", "user_id"], force: :cascade do |t|
+    t.integer "id"
+    t.integer "user_id"
     t.string "number", null: false
     t.string "semester", null: false
     t.string "title", null: false
-    t.integer "user_id", null: false
     t.string "personal_annotation"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
-    t.index ["number", "semester"], name: "index_favorite_courses_on_number_and_semester", unique: true
+    t.index ["user_id"], name: "index_favorite_courses_on_user_id"
   end
 
-  create_table "favorite_people", id: false, force: :cascade do |t|
+  create_table "favorite_people", primary_key: ["tiss_id", "user_id"], force: :cascade do |t|
     t.integer "tiss_id", null: false
-    t.integer "user_id", null: false
+    t.integer "user_id"
     t.string "first_name"
     t.string "last_name"
     t.string "picture_uri"
     t.string "personal_annotation"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
-    t.index ["tiss_id"], name: "index_favorite_people_on_tiss_id", unique: true
+    t.index ["user_id"], name: "index_favorite_people_on_user_id"
   end
 
-  create_table "favorite_projects", id: false, force: :cascade do |t|
+  create_table "favorite_projects", primary_key: ["id", "user_id"], force: :cascade do |t|
     t.integer "id", null: false
-    t.integer "user_id", null: false
+    t.integer "user_id"
     t.string "title"
     t.string "personal_annotation"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
-    t.index ["id"], name: "index_favorite_projects_on_id", unique: true
+    t.index ["user_id"], name: "index_favorite_projects_on_user_id"
   end
 
-  create_table "favorite_theses", id: false, force: :cascade do |t|
+  create_table "favorite_theses", primary_key: ["id", "user_id"], force: :cascade do |t|
     t.integer "id", null: false
-    t.integer "user_id", null: false
+    t.integer "user_id"
     t.string "title"
     t.string "personal_annotation"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
-    t.index ["id"], name: "index_favorite_theses_on_id", unique: true
+    t.index ["user_id"], name: "index_favorite_theses_on_user_id"
   end
 
   create_table "users", force: :cascade do |t|