docs: add a doc page on application sharing and user roles
** xref:management.adoc[Management]
*** xref:management.adoc#applications[Applications]
*** xref:management.adoc#devices[Devices]
+*** xref:management-app-members.adoc[Application sharing]
*** xref:management-rules.adoc[Event pre-processing]
*** xref:management-mqtt.adoc[MQTT dialects]
** Endpoints
