Do not show the Add to Filters action button if the filter exists

[joey-grafana]

Fixes #123

[adrapereira]

I have one comment which greatly impacts the feature, so can't approve yet. The approach makes sense though!

We might have to make the logic to check if the filter exists a bit smarter, for example if the existing filter operator is = or =~ say filter exists, otherwise check if key and value match.

[adrapereira]

We're only checking if the label/key matches, which means that we can't build queries like { foo != "abc" && foo != "xyz" }. We don't have include/exclude buttons for now but we might add them soon and the ability to exclude multiple values for the same attribute may be useful.

[joey-grafana]

Good point, update to follow

[ifrost]

Works great!

Out of curiosity - why name of the field is wrapped in " and forces us to sanitize it with value.replace(/"/g, '')?

[adrapereira]

@ifrost I cleaned this up a bit in my exemplars PR which will only wrap it in quotes when absolutely needed.

The reason is that Tempo is aware of the type of the values, so the value "123" is a string and 123 is a number. In order to keep it accurate and differentiate this in graphs we wrap strings in quotes.

approved but forgotten