feat: added interpolation to the prefix property of gcp_cloud_storage.

[paulosimao-ardanlabs]

This PR adds interpolation to the prefix property of gcp_cloud_storage. Although there are no messages in context at this stage (so we have only bloblang expressions), it seems to be more ergonomic to deal with dynamic file filtering as input.

[jem-davies]

Suggested change

	Description("An optional path prefix, if set only objects with the prefix are consumed - supports interpolation.").
	Description("An optional path prefix, if set only objects with the prefix are consumed.").

NewInterpolatedStringField will append a sentence to the Description - you can see it in website/docs/components/inputs/gcp_cloud_storage.md

[paulosimao-ardanlabs]

Thanks - fixed.

[jem-davies]

Think will need to have a think about allowing a bloblang interpolation on an input component, because of the issue about not having a message to execute it against.

[jem-davies]

I think we might need wider thinking about how we can enable the flexibility of bloblang interpolations to input components, more generally. imo.

Perhaps we should just add a section about it, to the page

[jem-davies]

Thanks for the PR - question: Are you able to give an example config where you are using this / what use-case does this change solve?

[paulosimao-ardanlabs]

Thanks for the PR - question: Are you able to give an example config where you are using this / what use-case does this change solve?

Most of the time is used for dealing with dates in the path, like this: /path/date=${!(timestamp_unix()-(26060)).format_timestamp_strftime("%Y-%m-%d-%H")}

Or setting prefix based on other conditions - this could have been addressed with env vars - but the team finds it way more ergonomic, and we already have a good amount of pipelines like this.