feat: support any response type

lib/apia/response.rb

@@ -71,11 +71,10 @@ def body
     # @return [Array]
     def rack_triplet
       # Errors will always be sent as a hash intended for JSON encoding,
-      # even if the endpoint specifies a plain text response, so only
-      # send a pain response if the type is plaintext _and_ the body is
-      # a string
-      if @type == PLAIN && body.is_a?(String)
-        Rack.plain_triplet(body, headers: headers, status: status)
+      # even if the endpoint specifies a non-JSON response, so only send a
+      # plain response if the type is not JSON _and_ the body is a string.
+      if @type != JSON && body.is_a?(String)
+        Rack.response_triplet(body, content_type: @type, headers: headers, status: status)
       else
         Rack.json_triplet(body, headers: headers, status: status)
       end

spec/specs/apia/response_spec.rb

@@ -145,6 +145,26 @@
       end
     end
 
+    context 'with an arbitrary response type' do
+      let(:endpoint) do
+        Apia::Endpoint.create('ExampleEndpoint') { response_type 'text/vnd.turbo-stream.html' }
+      end
+
+      it 'should provide the configured content-type and return the body as-is' do
+        response = Apia::Response.new(request, endpoint)
+        response.body = '<turbo-stream></turbo-stream>'
+        expect(response.rack_triplet[1]['content-type']).to eq 'text/vnd.turbo-stream.html'
+        expect(response.rack_triplet[2][0]).to eq '<turbo-stream></turbo-stream>'
+      end
+
+      it 'should fall back to JSON if the body is not a string' do
+        response = Apia::Response.new(request, endpoint)
+        response.body = { hello: 'world' }
+        expect(response.rack_triplet[1]['content-type']).to eq 'application/json'
+        expect(response.rack_triplet[2][0]).to eq '{"hello":"world"}'
+      end
+    end
+
     context 'with a legacy plain text response' do
       it 'should return 200 by default' do
         endpoint = Apia::Endpoint.create('ExampleEndpoint')