User-selectable default profile for requests

[zwimer]

Description

It'd be nice to allow individual users to select their preferred default profile.

Some examples of how this might be useful:

1. User wants to set a profile without bothering Admin
2. User's primary language differs from Admin's and mostly selects a different profile for requests. (Admin could force a profile via an override rule, but that removes user choice in profile selection and forces a profile they might not want for all requests).
3. User wants to change the profile used by the plex watchlist monitoring feature
4. User's primary device does not support something like HDR so they prefer their default profile not to allow such things, but for their favorite media they use a different device and want HDR (Override rules would force exactly one or the other if used)

Desired Behavior

Allow individual users to select their preferred default profile so they don't have to change it to whatever it is they want on every single request (also so that plex watchlist requests use this as lacking this may otherwise render the watchlist watching feature useless).

Additional Context

Currently, admins can do per-user profiles via override rules, but this overrides all requests rather than just being a default, and also requires the admin to act rather than letting an individual user set their preferred default.

Related but insufficient:
#757 (This PR might have solved the issue, but was closed in favor of override rules)
#921

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[fallenbagel]

Cant you just give your users advanced request permission so they can select what profile they want...

[zwimer]

In some cases, but since it has to be selected each time and thus cannot be done for Plex watchlist grabbing. Meaning users who want to use that feature but want to grab items in the non-default profile need to have an override rule, which also forces the override for manually requested items as well. So for these users, not having this can be a deal-breaker for using the plex watchlist feature.

For users who don't use Plex watchlist requests, this is just a matter of making sure they don't keep forgetting to change it with every request then ping the admin when they later discover the wrong profile was used. This is more of a quality of life improvement, for both the users and the pinged admins.