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

app/models/favorite_course.rb

@@ -1,4 +1,6 @@
 class FavoriteCourse < ApplicationRecord
+  self.primary_keys = :id, :user_id
+
   validates :title, :semester, :number, presence: true
-  validates :semester, :number, uniqueness: {scope: [:semester, :number]}
+  validates :semester, :number, uniqueness: {scope: [:semester, :number, :user_id]}
 end

app/models/favorite_person.rb

@@ -1,5 +1,5 @@
 class FavoritePerson < ApplicationRecord
-  self.primary_key = 'tiss_id'
+  self.primary_keys = :tiss_id, :user_id
 
-  validates :tiss_id, uniqueness: true
+  validates :tiss_id, uniqueness: { scope: [:user_id] }
 end

app/models/favorite_project.rb

@@ -1,5 +1,5 @@
 class FavoriteProject < ApplicationRecord
-  self.primary_key = 'id'
+  self.primary_keys = :id, :user_id
 
-  validates :id, uniqueness: true
+  validates :id, :user_id, uniqueness: {scope: [:id, :user_id]}
 end

app/models/favorite_thesis.rb

@@ -1,5 +1,5 @@
 class FavoriteThesis < ApplicationRecord
-  self.primary_key = 'id'
+  self.primary_keys = :id, :user_id
 
-  validates :id, uniqueness: true
+  validates :id, :user_id, uniqueness: {scope: [:id, :user_id]}
 end