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