Accept full URLs

It looks like the intention was there, so I made it work.
I've included a real world example, but added capitalisation to complete the test.

app/models/enterprise.rb

@@ -450,7 +450,8 @@ class Enterprise < ApplicationRecord
   end
 
   def strip_url(url)
-    url&.sub(%r{(https?://)?}, '')
+    # Strip protocol and trailing slash
+    url&.sub(%r{(https?://)?}, '')&.sub(%r{/\z}, '')
   end
 
   def correct_whatsapp_url(phone_number)

spec/models/enterprise_spec.rb

@@ -171,8 +171,8 @@ describe Enterprise do
         expect(e).to_not be_valid
       end
 
-      it "invalidates the instagram attribute https://instagram.com/user/" do
-        e = build(:enterprise, instagram: 'https://instagram.com/user/')
+      it "invalidates the instagram attribute https://www.instagram.com/p/Cpg4McNPyJA/" do
+        e = build(:enterprise, instagram: 'https://www.instagram.com/p/Cpg4McNPyJA/')
         expect(e).to_not be_valid
       end
 

spec/system/consumer/registration_spec.rb

@@ -117,8 +117,8 @@ describe "Registration" do
       click_button "Continue"
       expect(page).to have_content 'How can people find My Awesome Enterprise online?'
 
-      # Filling in social with invalid value for instagram - slash after InStAgRaM
-      fill_in "enterprise_instagram", with: 'www.instagram.com/InStAgRaM/'
+      # Filling in social with invalid value for instagram - a link to a post instead of user
+      fill_in "enterprise_instagram", with: 'https://www.instagram.com/p/Cpg4McNPyJA/'
       accept_alert "Failed to update your enterprise." do
         click_button "Continue"
       end
@@ -129,7 +129,7 @@ describe "Registration" do
       fill_in 'enterprise_facebook', with: 'FaCeBoOk'
       fill_in 'enterprise_linkedin', with: 'LiNkEdIn'
       fill_in 'enterprise_twitter', with: 'https://www.twitter.com/@TwItTeR'
-      fill_in 'enterprise_instagram', with: 'www.instagram.com/InStAgRaM'
+      fill_in 'enterprise_instagram', with: 'https://www.instagram.com/OpenFoodNetwork/'
       click_button "Continue"
       expect(page).to have_content 'Finished!'
 
@@ -147,7 +147,7 @@ describe "Registration" do
       expect(e.facebook).to eq "FaCeBoOk"
       expect(e.linkedin).to eq "LiNkEdIn"
       expect(e.twitter).to eq "TwItTeR"
-      expect(e.instagram).to eq "instagram"
+      expect(e.instagram).to eq "openfoodnetwork"
 
       click_link "Go to Enterprise Dashboard"
       expect(page).to have_content "CHOOSE YOUR PACKAGE"