FIX: handle quote rendering for external Discourse instance (#16722)

Gracefully handle quotes from an external discourse instance by stripping quote-controls and including username in the title

spec/lib/quote_comparer_spec.rb

@@ -4,6 +4,30 @@ require 'quote_comparer'
 
 describe QuoteComparer do
 
+  describe "#missing?" do
+    fab!(:post) { Fabricate(:post, raw: "This has **text** we _are_ matching") }
+
+    it "returns true for missing topic and post" do
+      expect(QuoteComparer.new(nil, nil, "test")).to be_missing
+    end
+
+    it "returns true for missing topic" do
+      expect(QuoteComparer.new(nil, post.post_number, "test")).to be_missing
+    end
+
+    it "returns true for missing post" do
+      expect(QuoteComparer.new(post.topic_id, nil, "test")).to be_missing
+    end
+
+    it "returns false for only missing text" do
+      expect(QuoteComparer.new(post.topic_id, post.post_number, nil)).to_not be_missing
+    end
+
+    it "returns false for no missing topic and post" do
+      expect(QuoteComparer.new(post.topic_id, post.post_number, "test")).to_not be_missing
+    end
+  end
+
   describe "#modified?" do
     fab!(:post) { Fabricate(:post, raw: "This has **text** we _are_ matching") }
 
@@ -11,10 +35,6 @@ describe QuoteComparer do
       QuoteComparer.new(post.topic_id, post.post_number, text)
     end
 
-    it "returns true for no post" do
-      expect(QuoteComparer.new(nil, nil, "test")).to be_modified
-    end
-
     it "returns true for nil text" do
       expect(qc(nil)).to be_modified
     end