Prepare Mastodon for Rails 6 (#15911)

* Fix misuse of foreign_type

* Fix use of removed "add_template_helper"

* Use response.media_type instead of response.content_type in tests

* Fix CSV export controller test on Rails 6

Rails 6 sets a "filename*" field in the Content-Disposition header to
explicitly encode the filename as UTF-8.

This changes checks the first part of the Content-Disposition header so
it matches in both Rails 5 and Rails 6.

* Fix emoji formatting with Rails 6

* Make emoji output more idiomatic and robust

* Switch from redis-rails gem to built-in Rails redis cache storage

3 files changed, 6 insertions, 6 deletions

diff --git a/spec/requests/catch_all_route_request_spec.rb b/spec/requests/catch_all_route_request_spec.rb
index 22ce1cf59..f965f5522 100644
--- a/spec/requests/catch_all_route_request_spec.rb
+++ b/spec/requests/catch_all_route_request_spec.rb
@@ -6,7 +6,7 @@ describe "The catch all route" do
       get "/test"
 
       expect(response.status).to eq 404
-      expect(response.content_type).to eq "text/html"
+      expect(response.media_type).to eq "text/html"
     end
   end
 
@@ -15,7 +15,7 @@ describe "The catch all route" do
       get "/test.test"
 
       expect(response.status).to eq 404
-      expect(response.content_type).to eq "text/html"
+      expect(response.media_type).to eq "text/html"
     end
   end
 end
diff --git a/spec/requests/host_meta_request_spec.rb b/spec/requests/host_meta_request_spec.rb
index beb33a859..0ca641461 100644
--- a/spec/requests/host_meta_request_spec.rb
+++ b/spec/requests/host_meta_request_spec.rb
@@ -6,7 +6,7 @@ describe "The host_meta route" do
       get host_meta_url
 
       expect(response).to have_http_status(200)
-      expect(response.content_type).to eq "application/xrd+xml"
+      expect(response.media_type).to eq "application/xrd+xml"
     end
   end
 end
diff --git a/spec/requests/webfinger_request_spec.rb b/spec/requests/webfinger_request_spec.rb
index 48823714e..209fda72a 100644
--- a/spec/requests/webfinger_request_spec.rb
+++ b/spec/requests/webfinger_request_spec.rb
@@ -8,7 +8,7 @@ describe 'The webfinger route' do
       get webfinger_url(resource: alice.to_webfinger_s)
 
       expect(response).to have_http_status(200)
-      expect(response.content_type).to eq 'application/jrd+json'
+      expect(response.media_type).to eq 'application/jrd+json'
     end
   end
 
@@ -17,7 +17,7 @@ describe 'The webfinger route' do
       get webfinger_url(resource: alice.to_webfinger_s, format: :json)
 
       expect(response).to have_http_status(200)
-      expect(response.content_type).to eq 'application/jrd+json'
+      expect(response.media_type).to eq 'application/jrd+json'
     end
 
     it 'returns a json response for json accept header' do
@@ -25,7 +25,7 @@ describe 'The webfinger route' do
       get webfinger_url(resource: alice.to_webfinger_s), headers: headers
 
       expect(response).to have_http_status(200)
-      expect(response.content_type).to eq 'application/jrd+json'
+      expect(response.media_type).to eq 'application/jrd+json'
     end
   end
 end