Loki: Ability to search for value in label browser without needing to pre-select labels to search in

[ivanahuckova]

When using Loki's label browser, users have to pre-select labels in which they want to fins specified value. This is because there is no API in Loki that would help us with this.

Users would like a way how to search for value without needing to pre-select labels to search in.

[liguozhong]

This is a very important feature. 👍

We can add a default label configuration to the loki datasource configuration. The value is usually: {type="system"} or {env="pro"}.

When user open log explorer for the first time, if the selected loki datasource default label config is not empty, the value of the logql search box will be filled in by default label or it will prompt that no label is currently selected. We will use the default label as the search condition to search for you.