WIP on docs/theory

Co-authored-by: Roberto Abdelkader Martínez Pérez <robertomartinezp@gmail.com>

docs/source/theory/request_life_cycle.rst

@@ -4,4 +4,26 @@ Request Life Cycle
 This section describes the sequence of events happening for each request
 answered by the User HTTP Interface.
 
+#. The user makes a request to the User HTTP Interface
 
+#. The request is matched against the route table
+
+#. Kapow! provides a HANDLER_ID to identify this request
+
+#. Kapow! spawns the binary specified as entrypoint in the matching route
+
+   The default entrypoint is /bin/sh; we'll explain this workflow for now.
+
+   The spawned entrypoint is run with following variables added to its environment:
+- KAPOW_HANDLER_ID
+- KAPOW_DATAAPI_URL
+- KAPOW_CONTROLAPI_URL
+
+#.  During the lifetime of the shell, the request and response resources are available via these commands:
+
+- kapow get /request/...
+- kapow set /response/...
+
+TODO: link to resource tree
+
+#. When the shell dies, Kapow! finalizes the original request.