DataLinks: enable access to labels & field names (#18918)

* POC: trying to see if there is a way to support objects in template interpolations

* Added support for nested objects, and arrays

* Added accessor cache

* fixed unit tests

* First take

* Use links supplier in graph

* Add field's index to cache items

* Get field index from field cache

* CHange FiledCacheItem to FieldWithIndex

* Add refId to TimeSeries class

* Make field link supplier work with _series, _field and _value vars

* use field link supplier in graph

* Fix yaxis settings

* Update dashboard schema version and add migration for data links variables

* Update snapshots

* Update build in data link variables

* FieldCache - idx -> index

* Add current query results to panel editor

* WIP Updated data links dropdown to display new variables

* Fix build

* Update variables syntac in field display, update migration

* Field links supplier: review updates

* Add data frame view and field name to TimeSeries for later inspection

* Retrieve data frame from TimeSeries when clicking on plot graph

* Use data frame's index instead of view

* Retrieve data frame by index instead of view on TimeSeries

* Update data links prism regex

* Fix typecheck

* Add value variables to suggestions list

* UI update

* Rename field to config in DisplayProcessorOptions

* Proces single value of a field instead of entire data frame

* Updated font size from 10px to 12px for auto complete

* Replace fieldName with fieldIndex in TimeSeries

* Don't use .entries() for iterating in field cache

* Don't use FieldCache when retrieving field for datalinks in graph

* Add value calculation variable to data links (#19031)

* Add support for labels with dots in the name (#19033)

* Docs update

* Use field name instead of removed series.fieldName

* Add test dashboard

* Typos fix

* Make visualization tab subscribe to query results

* Added tags to dashboard so it shows up in lists

* minor docs fix

* Update singlestat-ish variables suggestions to contain series variables

* Decrease suggestions update debounce

* Enable whitespace characters(new line, space) in links and strip them when processing the data link

* minor data links UI update

* DataLinks: Add __from and __to variables suggestions to data links (#19093)

* Add from and to variables suggestions to data links

* Update docs

* UI update and added info text

* Change ESC global bind to bind (doesn't capture ESC on input)

* Close datalinks suggestions on ESC

* Remove unnecessary fragment

docs/sources/features/panels/graph.md

@@ -192,7 +192,7 @@ Panel time overrides & timeshift are described in more detail [here]({{< relref
 
 > Only available in Grafana v6.3+.
 
-Data link in graph settings allows adding dynamic links to the visualization. Those links can link to either other dashboard or to an external URL.
+Data link allows adding dynamic links to the visualization. Those links can link to either other dashboard or to an external URL.
 
 {{< docs-imagebox img="/img/docs/data_link.png"  max-width= "800px" >}}
 
@@ -208,14 +208,40 @@ available suggestions:
 {{< docs-imagebox img="/img/docs/data_link_typeahead.png"  max-width= "800px" >}}
 
 
-Available built-in variables are:
+#### Built-in variables
 
-1. ``__all_variables`` - will add all current dashboard's variables to the URL
-2. ``__url_time_range`` - will add current dashboard's time range to the URL (i.e. ``?from=now-6h&to=now``)
-3. ``__series_name`` - will add series name as a query param in the URL (i.e. ``?series=B-series``)
-4. ``__value_time`` - will add datapoint's timestamp (Unix ms epoch) to the URL (i.e. ``?time=1560268814105``)
+``__url_time_range`` - current dashboard's time range (i.e. ``?from=now-6h&to=now``)
+``__from`` - current dashboard's time range from value
+``__to`` - current dashboard's time range to value
+
+#### Series variables
+Series specific variables are available under ``__series`` namespace:
+
+``__series.name`` - series name to the URL
+
+``__series.labels.<LABEL>`` - label's value to the URL. If your label contains dots use ``__series.labels["<LABEL>"]`` syntax
+
+#### Field variables
+Field specific variables are available under ``__field`` namespace:
+
+``__field.name`` - field name to the URL
+
+#### Value variables
+Value specific variables are available under ``__value`` namespace:
+
+``__value.time`` - value's timestamp (Unix ms epoch) to the URL (i.e. ``?time=1560268814105``)
+
+``__value.raw`` - raw value
+
+``__value.numeric`` - numeric representation of a value
+
+``__value.text`` - text representation of a value
+
+``__value.calc`` - calculation name if the value is result of calculation
 
 
-#### Template variables in data links
+
+#### Template variables
+
 When linking to another dashboard that uses template variables, you can use ``var-myvar=${myvar}`` syntax (where ``myvar`` is a name of template variable)
-to use current dashboard's variable value.
+to use current dashboard's variable value. If you want to add all of the current dashboard's variables to the URL use  ``__all_variables`` variable.