feat: properly export env vars for cnb apps

They are not baked into the image like they are for herokuish, so we need to manually set them via --env. Additionally, due to newline constraints in docker, we need to use `--env=key` format to correctly pull the values into place.

tests/apps/python/web.py

@@ -1,4 +1,5 @@
 import http.server
+import json
 import os
 
 
@@ -7,7 +8,12 @@ class GetHandler(http.server.BaseHTTPRequestHandler):
         self.send_response(200)
         self.send_header("Content-Type", "text/plain; charset=utf-8")
         self.end_headers()
-        self.wfile.write("python/http.server".encode("utf-8"))
+
+        if self.path == '/':
+            self.wfile.write("python/http.server".encode("utf-8"))
+        else:
+            data = json.dumps(dict(os.environ), sort_keys=True, indent=4)
+            self.wfile.write(data.encode("utf-8"))
 
 
 if __name__ == "__main__":