Add remove from followers api (#16864)

* Add followed_by? to account_interactions

* Add RemoveFromFollowersService

* Fix AccountBatch to use RemoveFromFollowersService

* Add remove from followers API

spec/controllers/api/v1/accounts_controller_spec.rb

@@ -168,6 +168,26 @@ RSpec.describe Api::V1::AccountsController, type: :controller do
     it_behaves_like 'forbidden for wrong scope', 'read:accounts'
   end
 
+  describe 'POST #remove_from_followers' do
+    let(:scopes) { 'write:follows' }
+    let(:other_account) { Fabricate(:user, email: 'bob@example.com', account: Fabricate(:account, username: 'bob')).account }
+
+    before do
+      other_account.follow!(user.account)
+      post :remove_from_followers, params: { id: other_account.id }
+    end
+
+    it 'returns http success' do
+      expect(response).to have_http_status(200)
+    end
+
+    it 'removes the followed relation between user and target user' do
+      expect(user.account.followed_by?(other_account)).to be false
+    end
+
+    it_behaves_like 'forbidden for wrong scope', 'read:accounts'
+  end
+
   describe 'POST #block' do
     let(:scopes) { 'write:blocks' }
     let(:other_account) { Fabricate(:user, email: 'bob@example.com', account: Fabricate(:account, username: 'bob')).account }