Option to set "on completion: delete" as default

[GrayStrider]

⚠️ Please check that this feature request hasn't been suggested before.

• I searched previous Ideas in Discussions didn't find any similar feature requests.
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• I am only requesting a single feature. Multiple changes should be split into individual requests, with links between them.
• I believe my requested feature will be generally applicable to other users, not just me: it is not uniquely tied to my personal workflow.

🔖 Feature description

Option to set "on completion: delete" as default in extension settings

✔️ Solution

Would save time for users that create mostly one-off tasks and do not wish to keep them after completion.

❓ Alternatives

Input "on completion: delete" manually every time

📝 Additional Context

Currently, "on completion: keep" is treated as default, same as not having that flag at all.

[claremacrae]

I have been mulling this over.

I understand the desire to apply "on completion: delete" more easily than on every task line.

However, I am not comfortable enabling an option for it, as it then requires users to remember to add 'keep', making it too dangerous a facility to supply.

There is, however, an existing request that would offer an alternative idea:

• Apply properties to all tasks in a file via YAML frontmatter #3090

Once implemented, that would allow frontmatter such as something like this:

tasks-default-on-completion: delete

The Obsidian properties editor would make it very easy to add this to individual markdown notes.

And users who wanted it add it everywhere could set up a default template for their notes, that included that property on every new page.