profiles: claws-mail: add cache support

[glitsj16]

Add support for the (widely used) Fancy plugin:
Renders HTML e-mail using the WebKit library

https://www.claws-mail.org/plugins.php

Related to #6377.

[kmk3]

email-common contains private-cache, so wouldn't these changes be a no-op?

Does the plugin not work with the current profile?

[glitsj16]

email-common contains private-cache, so wouldn't these changes be a no-op?

You're absolutely right. This PR makes no sense, my bad.

[kmk3]

email-common contains private-cache, so wouldn't these changes be a no-op?

You're absolutely right. This PR makes no sense, my bad.

I was confused about the plugin not working without the changes, but the
changes themselves seem fine (if they are indeed a no-op with private-cache).

It seems good for documentation purposes, to have it blocked in
disable-programs and to make it easier to use the real cache directory (by just
using ignore private-cache).

[kmk3]

@glitsj16

Hello, do you want to continue with this PR?

It's likely possible to click to restore the branch and then to reopen the PR.

[glitsj16]

@kmk3

Hi, I'll take care of it today. Last days of school exams here, less computer-time for me usually. But it shouldn't take that long to restore and reopen this. Thanks for the reminder!

[kmk3]

Hi, I'll take care of it today. Last days of school exams here, less
computer-time for me usually. But it shouldn't take that long to restore and
reopen this. Thanks for the reminder!

Ah I see, I wasn't sure if you had seen previous comment, so I commented again
just in case.

Anyway, no hurry on the PR.

Good luck on the exams!

[kmk3]

Why the new changes?

It seems like the version from yesterday would work and make it easier to use
the real cache directory if desired.

[glitsj16]

@kmk3

Why the new changes?

Oh, I misunderstood. Thought you'd only wanted to keep the disable-common.inc part and leave private-cache as-is. To avoid more mishaps from my side, do you think it would make more sense to ignore private-cache for CM and use the dedicated whitelisted ~/.cache/claws-mail instead?

[kmk3]

To avoid more mishaps from my side, do you think it would make more sense to
ignore private-cache for CM and use the dedicated whitelisted
~/.cache/claws-mail instead?

I think in general it's good to leave private-cache on by default to help
keep sandboxes isolated and to avoid unecessarily reducing the lifespan of
storage devices, as IME programs rarely make good use of ~/.cache.

The exceptions would be if the program creates a giant cache (which like
private-opt could take too much RAM) or when caching actually makes a
positive noticeable difference (like shader caches in certain programs).

Edit: To be clear, I think that the original changes were correct (with the
whitelist and without ignore private-cache).