Added join requests to Groups

• Added:
- join requests to Groups
- redux actions, reducers
- controller and functionality for fetching join requests, accepting, rejecting join requests

app/models/concerns/group_interactions.rb

@@ -17,6 +17,10 @@ module GroupInteractions
       follow_mapping(GroupAccount.where(group_id: target_group_ids, account_id: account_id, role: :moderator), :group_id)
     end
 
+    def requested_map(target_group_ids, account_id)
+      follow_mapping(GroupJoinRequest.where(group_id: target_group_ids, account_id: account_id), :group_id)
+    end
+
     def pinned?(status)
       group_pinned_statuses.where(group_id: status.group_id, status: status).exists?
     end

app/models/group.rb

@@ -35,6 +35,9 @@ class Group < ApplicationRecord
 
   has_many :group_accounts, inverse_of: :group, dependent: :destroy
   has_many :accounts, through: :group_accounts
+  
+  has_many :group_join_requests, inverse_of: :group, dependent: :destroy
+  has_many :join_requests, source: :account, through: :group_join_requests
 
   has_many :group_pinned_statuses, inverse_of: :group, dependent: :destroy
   has_many :pinned_statuses, source: :status, through: :group_pinned_statuses

app/models/group_join_request.rb

@@ -0,0 +1,17 @@
+# == Schema Information
+#
+# Table name: group_join_requests
+#
+#  id         :bigint(8)        not null, primary key
+#  account_id :bigint(8)        not null
+#  group_id   :bigint(8)        not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class GroupJoinRequest < ApplicationRecord
+  belongs_to :group
+  belongs_to :account
+
+  validates :account_id, uniqueness: { scope: :group_id }
+end