Fix subscriptions via REST when using params

[frankosterfeld]

Unify subscription topic handling and fix it for REST (#328, #331)

Do not lose params when subscribing to a topic via REST.

Bump cpp-httplib to newest version, as it fixes an encoding error with query parameters encoded in query parameters (SubscriptionContext) when used with redirects.

To unify subscription handling (different client/servers were making slightly different assumptions), the following is now implemented:

• Service names must always start with "/".
• The topic is of the form "/some/service?param1=..&param2", where the service name is mandatory in the topic, and the params are optional.
  • When serialized to a ZMQ topic, i.e. the string-based PUB/SUB topic matching, the parameters are sorted, to make the subscription and notification topics match exactly (required by ZMQ, as ZMQ subscription topics are string-, not URI-based)
  • Valid REST URIs are e.g. "http://localhost:8080/service?a&b" or http://localhost:8080/service?a&b", i.e. the service is a mandatory part of the URI. mds:// and mdp:// URIs are analogous.
  • On the ZMQ message level, the "serviceName" in above examples would be "/service" and the "topic" would be "/service?a&b" (here param order is not enforced).

UPDATE: Rebased/merged #330 into this one:

Make sure that long-poll request handlers do not block forever when no corresponding event is received. Otherwise the clients will send one request after another once their request times out client-side, until the worker threads are exhausted and the server stops responding.

It would be great if we could also detect the client connection be dropped using Keep-Alive, but cpp-httplib doesn't seem to have API for that.

[codecov[bot]]

Codecov Report

Attention: 171 lines in your changes are missing coverage. Please review.

Comparison is base (99ae7d2) 55.84% compared to head (a03822f) 57.15%.

Files	Patch %	Lines
src/majordomo/include/majordomo/RestBackend.hpp	36.58%	18 Missing and 34 partials :warning:
src/majordomo/include/majordomo/Broker.hpp	35.29%	3 Missing and 30 partials :warning:
src/client/include/RestClientNative.hpp	15.15%	14 Missing and 14 partials :warning:
src/core/include/Topic.hpp	70.00%	1 Missing and 20 partials :warning:
src/client/include/Client.hpp	14.28%	2 Missing and 16 partials :warning:
src/majordomo/include/majordomo/Worker.hpp	39.13%	3 Missing and 11 partials :warning:
src/client/include/MockServer.hpp	40.00%	0 Missing and 3 partials :warning:
src/zmq/include/zmq/ZmqUtils.hpp	0.00%	0 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #331 +/- ## ========================================== + Coverage 55.84% 57.15% +1.30% ========================================== Files 69 69 Lines 7291 7310 +19 Branches 2691 2703 +12 ========================================== + Hits 4072 4178 +106 + Misses 1484 1322 -162 - Partials 1735 1810 +75 ```

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[sonarcloud[bot]]

Quality Gate failed

Failed conditions

35.3% Coverage on New Code (required ≥ 80%)
17.9% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud