Textarea inside a tabs component mutates a multiline value

[samuelhwilliams]

Describe the bug
When one of the items passed into a tabs component is a textarea, with a value that has a multiline string, the textarea input gets indented.

https://github.com/LandRegistry/govuk-frontend-jinja/blob/main/govuk_frontend_jinja/templates/components/tabs/macro.html#L45
https://github.com/LandRegistry/govuk-frontend-jinja/blob/main/govuk_frontend_jinja/templates/components/tabs/macro.html#L19

It is seemingly not safe to use indent() on textareas, because it can change the value passed in.

To Reproduce
Steps to reproduce the behavior:

1. Setup a wtform with a stringfield using a govuktextarea widget.
2. Instantiate the form and pass some multiline text data to the field
3. Render the textarea using govukTextarea inside a govukTabs component.
4. See that lines 2+ are prefixed with 4 spaces.

Expected behavior
The value of the textarea is not changed by rendering it inside a tabs component.

Screenshots

With native govuk-frontend-jinja macro

With modified govuk-frontend-jinja macro (all indent() calls removed)