DEV: Use site setting mandatory_values for chat allowed groups

[martin-brennan]

For both chat_allowed_groups and chat_message_flag_allowed_groups,
this commit removes the is_staff? guardian check, and instead
adds both moderators and admins auto groups as mandatory_values
to those settings, as part of an ongoing effort to do this for
group-based setting values.

[SamSaffron]

I like this, but does this need any kind of migration? what happens to existing site settings here that don't have it set?

[martin-brennan]

@SamSaffron No it's not necessary; the way this mandatory_values code works is that it injects these values no matter what, both in the get and the set for the site setting. So if you call SiteSetting.chat_allowed_groups, and the database already had group 99|76 in it, you would get back 1|2|99|76. And if you did SiteSetting.chat_allowed_groups = "54" we save the mandatory values too, so you will also get back SiteSetting.chat_allowed_groups => '1|2|54'

[SamSaffron]

approved but just double checking, will this handle duplication?

[martin-brennan]

will this handle duplication?

@SamSaffron as in, if I do SiteSetting.chat_allowed_groups = "54" multiple times it won't keep adding 1|2 on forever until we get 1|2|1|2|1|2|1|2|1|2? If so yes that was handled by Kris when he made this mandatory values thing :)

[discoursebot]

This pull request has been mentioned on Discourse Meta. There might be relevant details there:

https://meta.discourse.org/t/mandatory-fields-for-group-site-setting/307219/2