Hardening/libcurl

**DON'T MERGE**

Orion uses libcurl to send HTTP requests.
Regarding receiving buffer, it should be small, but we should protect anyway (imagine a malicious notification receiver designed to inject a 100MB payload in the 200 OK message to crash stress/crash the CB).

Regarding outgoing message, let's wait for your new after your research :). Note that the tests in notification_different_sizes.test area about outgoing buffer. Probaby we should also have tests for receiving buffer (although they would be more difficult to implement, as we need a mock prepared for that, an current accumulator-server.py is not able... maybe tests on receiving buffer should be scheduled in a new issue as tech debt).