Network API loccontrol should also handle a JSON body request

As `rules/add` does. In other words, the following should work:

```Shell
cat <

Start at the /api/sys/loccontrol handler and compare its request parsing with /api/loc/rules/add, which already accepts a JSON body. Reproduce the issue with the provided curl commands and verify that the direct JSON request produces the same result as the form-encoded control request, while the existing rules/add and events/ingest behavior remains unchanged.

Written by the indexing model from the issue text.