Handle nestings better and refactor asciidoc generation (#803)

* handle nestings better and refactor asciidoc generation

* update changelog

* linting

* move nesting logic to separate function and find re-nested fields

* better naming

* dont make asciidocs with subset or include options

* add docstrings

CHANGELOG.next.md

@@ -49,6 +49,7 @@ Thanks, you're awesome :-) -->
 #### Improvements
 
 * Add support for reusing offical fieldsets in custom schemas. #751
+* Add full path names to reused fieldsets in `nestings` array in ecs_nested.yml. #803
 
 #### Deprecated
 

docs/field-details.asciidoc

@@ -453,6 +453,12 @@ example: `co.uk`
 // ===============================================================
 
 
+| <<ecs-group,client.user.group.*>>
+| User's group relevant to the event.
+
+// ===============================================================
+
+
 |=====
 
 [[ecs-cloud]]
@@ -961,6 +967,12 @@ example: `co.uk`
 // ===============================================================
 
 
+| <<ecs-group,destination.user.group.*>>
+| User's group relevant to the event.
+
+// ===============================================================
+
+
 |=====
 
 [[ecs-dll]]
@@ -2692,6 +2704,12 @@ example: `1325`
 // ===============================================================
 
 
+| <<ecs-group,host.user.group.*>>
+| User's group relevant to the event.
+
+// ===============================================================
+
+
 |=====
 
 [[ecs-http]]
@@ -5292,6 +5310,12 @@ example: `co.uk`
 // ===============================================================
 
 
+| <<ecs-group,server.user.group.*>>
+| User's group relevant to the event.
+
+// ===============================================================
+
+
 |=====
 
 [[ecs-service]]
@@ -5627,6 +5651,12 @@ example: `co.uk`
 // ===============================================================
 
 
+| <<ecs-group,source.user.group.*>>
+| User's group relevant to the event.
+
+// ===============================================================
+
+
 |=====
 
 [[ecs-threat]]