feat (MQ): implement simple Stomp interface

docs/source/AdministratorGuide/Resources/index.rst

@@ -19,6 +19,7 @@ contributing with their computing and storage capacity, available as conventiona
    catalog
    computingelements
    messagequeues
+   simpleMQ
    storage
    agents2CS
    proxyprovider

docs/source/AdministratorGuide/Resources/simpleMQ.rst

@@ -0,0 +1,66 @@
+=====================
+Simple Message Queues
+=====================
+
+.. warning ::
+
+   Technology preview, will likely change interface
+
+
+The very abstracted implementation of MQ in DIRAC offers flexibility, but at the cost of complexity and limitations (multiple host behind a broker alias for example). A simpler implementation is proposed, but is still under development. At the moment, this simpler implementation only supports ``Stomp``, but that is the only one used so far.
+
+See :py:mod:`DIRAC.Resources.MessageQueue.Simple.StompInterface` for a more detailed documentation.
+
+How to migrate
+==============
+
+The configuration of the MQ can remain the same in the CS.
+
+The difference is in the code.
+
+.. code-block:: python
+
+  # Before
+  from DIRAC.Resources.MessageQueue.MQCommunication import createProducer, createConsumer
+
+  # New
+  from DIRAC.Resources.MessageQueue.Simple.StompInterface import createProducer, createConsumer
+
+
+The ``mqURI`` should also be changed to just the service name. For example
+
+.. code-block:: python
+
+  # Before
+  result = createProducer("Monitoring::Queues::dirac.monitoring")
+
+  # New
+  result = createProducer("Monitoring", destination="dirac.monitoring")
+  # or, if there is only one destination defined in the CS
+  # but this should be avoided
+  result = createProducer("Monitoring")
+
+
+The simpler interface can also listen to multiple destinations.
+
+.. code-block:: python
+
+  # Before
+  result = createConsumer("Monitoring::Queues::dirac.monitoring")
+
+  # New
+  result = createConsumer("Monitoring", destinations=["dirac.monitoring"])
+  # or, if no destination is specified, will listen to ALL the destinations
+  # in the CS
+  result = createProducer("Monitoring")
+
+
+There is however a compatibility layer, such that full ``mqURI`` are still accepted.
+
+Consumer are now driven by ``listener`` class instead of callback functions. Please see :py:mod:`DIRAC.Resources.MessageQueue.Simple.StompInterface` for example on how to use it
+
+
+
+.. warning ::
+
+  The generic implementation was always doing a ``json.dumps`` before sending, and always doing a ``json.loads`` when upon receiving. The simple interface does not do it. You have to manage the serialization yourself