Pass template_type through to alterMailing hook

[mattwire]

Overview

Follow on from #15306. Knowing the type of template (ie. traditional or mosaico) allows us to behave differently depending on the type of template.

Before

template_type available but not passed to hook.

After

template_type passed to hook.

Technical Details

Comments

@bhahumanists Please can you create a docs PR for this?

[civibot]

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[eileenmcnaughton]

@mattwire this seems fine - it's not a new hook or a significant change to the existing one - once you've addressed the needs-documentation go ahead & merge it.

[bhahumanists]

@mattwire done

[homotechsual]

Clear "needs-documentation".