Add alarm variables to the response of chart and data (#6615)

##### Summary
Implements feature #6054 

Now requests like 

http://localhost:19999/api/v1/chart?chart=example.random
http://localhost:19999/api/v1/data?chart=example.random&options=jsonwrap&options=showcustomvars

- return chart variables in their responses. Chart variables include only those with options set to RRDVAR_OPTION_CUSTOM_CHART_VAR
- for /api/v1/data requests chart variables are returned when parameter options=jsonwrap and options=showcustomvars

##### Component Name
[/database](https://github.com/netdata/netdata/tree/master/database/)
[/web/api/formatters](https://github.com/netdata/netdata/tree/master/web/api/formatters)

1 files changed, 8 insertions, 5 deletions

diff --git a/web/api/formatters/json_wrapper.c b/web/api/formatters/json_wrapper.c
index 4911d2f0ea..5ef2caf101 100644
--- a/web/api/formatters/json_wrapper.c
+++ b/web/api/formatters/json_wrapper.c
@@ -182,11 +182,14 @@ void rrdr_json_wrapper_begin(RRDR *r, BUFFER *wb, uint32_t format, RRDR_OPTIONS
 
     rrdr_buffer_print_format(wb, format);
 
-    buffer_sprintf(wb, "%s,\n"
-                       "   %sresult%s: "
-                   , sq
-                   , kq, kq
-    );
+    if((options & RRDR_OPTION_CUSTOM_VARS) && (options & RRDR_OPTION_JSON_WRAP)) {
+        buffer_sprintf(wb, "%s,\n   %schart_variables%s: ", sq, kq, kq);
+        health_api_v1_chart_custom_variables2json(r->st, wb);
+    }
+    else
+        buffer_sprintf(wb, "%s", sq);
+
+    buffer_sprintf(wb, ",\n   %sresult%s: ", kq, kq);
 
     if(string_value) buffer_strcat(wb, sq);
     //info("JSONWRAPPER(): %s: END", r->st->id);