#915 Add POST /task/add method

Adds the possibility to create a task with procedures and other tasks
integrated as steps.

Note: "steps" parameter is optional and "steps" array object order
defines execution order.

Request:
POST /task/add
{
  "center": "1",
  "name": "task",
  "description": "My task",
  "steps": [
             {
               "procedure": 4
             },
             {
               "task": 1
             },
             {
               "procedure": 24
             }
           ]
}

Response:
200 OK

This commit also add task case to procedure's step processing.
Otherwise, gcc prints the following warning:

src/rest.c: In function ‘og_procedure_add_steps’:
src/rest.c:4089:17: warning: enumeration value ‘OG_STEP_TASK’ not handled in switch [-Wswitch]
 4089 |                 switch (step->type) {
      |                 ^~~~~~

1 files changed, 1 insertions, 0 deletions

diff --git a/src/json.h b/src/json.h
index 1790d24..0d00679 100644
--- a/src/json.h
+++ b/src/json.h
@@ -105,6 +105,7 @@ struct og_cmd_json {
 enum og_procedure_step_type {
 	OG_STEP_COMMAND		= 0,
 	OG_STEP_PROCEDURE,
+	OG_STEP_TASK,
 };
 
 #define OG_PROCEDURE_STEPS_MAX	256