Support for Jax-RS style "StreamingOutput"

This commit only implements for the JEX server option.

Author: andponlin

http-api/src/main/java/io/avaje/http/api/StreamingOutput.java

@@ -0,0 +1,24 @@
+package io.avaje.http.api;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * An avaje {@link Controller} endpoint is able to use an instance of this interface
+ * as a return type.
+ *
+ * <pre>{@code
+ * @Post("some_endpoint")
+ * @Produces("application/octet-stream")
+ * public StreamingOutput thumbnail(
+ *   InputStream inputStream,
+ *   @QueryParam(Constants.KEY_SIZE) @Min(1) @Max(Constants.MAX_SIZE) Integer size
+ * ) throws IOException {
+ *   return (os) -> os.write(new byte[] { 0x01, 0x02, 0x03 });
+ * }
+ * }</pre>
+ */
+
+public interface StreamingOutput {
+  void write(OutputStream outputStream) throws IOException;
+}

http-generator-jex/src/main/java/io/avaje/http/generator/jex/ControllerMethodWriter.java

@@ -107,6 +107,7 @@ enum ResponseMode {
     Jstachio,
     Templating,
     InputStream,
+    StreamingOutput,
     Other
   }
 
@@ -117,6 +118,9 @@ ResponseMode responseMode() {
     if (isInputStream(method.returnType())) {
       return ResponseMode.InputStream;
     }
+    if (isStreamingOutput(method.returnType())) {
+      return ResponseMode.StreamingOutput;
+    }
     if (producesJson()) {
       return ResponseMode.Json;
     }
@@ -136,6 +140,10 @@ private boolean isInputStream(TypeMirror type) {
     return isAssignable2Interface(type.toString(), "java.io.InputStream");
   }
 
+  private boolean isStreamingOutput(TypeMirror type) {
+    return isAssignable2Interface(type.toString(), "io.avaje.http.api.StreamingOutput");
+  }
+
   private boolean producesJson() {
     return !"byte[]".equals(method.returnType().toString())
       && !useJstachio
@@ -294,11 +302,17 @@ private void writeContextReturn(ResponseMode responseMode, String resultVariable
       case Json -> writeJsonReturn(produces, indent);
       case Text -> writer.append("ctx.text(%s);", resultVariable);
       case Templating -> writer.append("ctx.html(%s);", resultVariable);
+      case StreamingOutput -> writeStreamingOutputReturn(produces, resultVariable, indent);
       default -> writer.append("ctx.contentType(\"%s\").write(%s);", produces, resultVariable);
     }
     writer.eol();
   }
 
+  private void writeStreamingOutputReturn(String produces, String resultVariable, String indent) {
+    writer.append("ctx.contentType(\"%s\");", produces).eol();
+    writer.append(indent).append("%s.write(ctx.outputStream());", resultVariable);
+  }
+
   private void writeJsonReturn(String produces, String indent) {
     var uType = UType.parse(method.returnType());
     boolean streaming = useJsonB && streamingContent(uType);