feat: add proxy template origin field and implement socket utilities for log streaming

templates/http-block-large-body.yaml

@@ -0,0 +1,37 @@
+id: http-block-large-body
+name: Block large request bodies
+protocol: http
+description: Rejects oversized HTTP request bodies before they hit the service.
+category: http
+family: web-hardening
+tags:
+- length-limit
+- body-size
+- web
+- block
+action: block
+summary: Rejects oversized HTTP request bodies before they hit the service.
+behavior: Checks the buffered request body length, returns 413 Payload Too Large,
+  and logs the observed size.
+source_url: https://docs.mitmproxy.org/stable/addons/examples/
+code: |
+  import logging
+
+  from mitmproxy import http
+
+  MAX_BODY_BYTES = 8192
+
+
+  def request(flow: http.HTTPFlow) -> None:
+      size = len(flow.request.raw_content or b"")
+      if size > MAX_BODY_BYTES:
+          logging.warning(
+              "[http-block-large-body] blocked %s bytes on %s",
+              size,
+              flow.request.pretty_url,
+          )
+          flow.response = http.Response.make(
+              413,
+              b"",
+              {"content-type": "text/plain"},
+          )