Support 'query' at the Elasticsearch scaler

[rickbrouwer]

Proposal

Making it possible to scale based on a direct Elasticsearch Query
To make this possible I introduce a new parameter query.

Use-Case

At the moment, the Elasticsearch scaler only supports the 'search template query'. As a result, you have to create templates first to be able to use them. First of all, this means that multiple 'search templates' have to be created and managed when you want to scale on multiple different queries.
In some organizations, such as where I work, the possibility to create a 'search template' lies with a separate team and not with the SRE teams. This makes it difficult to create or change the query's to use in the Elasticsearch scaler.

Being able to provide a Query gives you the freedom to create and change queries yourself to scale instead of creating search templates first.

Is this a feature you are interested in implementing yourself?

Yes

Anything else?

No response