go api: add nested and interleaved compression tests

Without tests or examples from the mod which produces these strings
we are unsure on if these types of compression ever actually can happen.

Given this, we want to add these as test cases to ensure we do not break
the possibly intended behavior.

backend/api/deck_test.go

@@ -52,11 +52,23 @@ func TestDecompress(t *testing.T) {
 			shouldError: false,
 		},
 		{
-			desc:        "Basic compression",
-			input:       "love|slay the||I &0 &0 &1 relics and &1 spire",
+			desc:        "Nested compression succeeds",
+			input:       "love|the|slay &1||I &0 &0 &2 relics and &2 spire",
 			output:      "I love love slay the relics and slay the spire",
 			shouldError: false,
 		},
+		{
+			desc:        "Interleaved compression succeeds",
+			input:       "AAA|BBB&|0CCC||&1&2",
+			output:      "BBBAAACCC",
+			shouldError: false,
+		},
+		{
+			desc:        "Interleaved repeated compression fails",
+			input:       "AAA|BBB&|1CCC||&1&2",
+			output:      "BBB&1CCC",
+			shouldError: false,
+		},
 		{
 			desc:        "Small Deck",
 			input:       "card|junk||0,1,1,0,2,0;;;&01;&1;x;;&02;&1;y;;&03;&1;z",