fixes#1958
Adds 2 new options:
* Do not allow stores to use the email settings of the server. Instead, they would need to fill in the email settings in their own store
* Do not allow user creation through the API unless you are an admin.
Both are opt-in and turned off by default.
The [previously used U2F library](https://github.com/fido-alliance/google-u2f-ref-code/) has been deprecated. The new one does not override the browsers `window.u2f` functionality if it is natively supported. It also displays the appropriate errors and falls back nicely in case the browser does not support U2F.
This allows plugins to create custom dbcontexts, which would be namespaced in the scheme with a prefix. Migrations are supported too and the table would be prefixed too
* Plugins: Load plugins by order, aesthetic plugin dependency system
Introduces plugins loading in order of installation, BTCPay itself shows up as a system plugin, and that plugins can define other plugins as dependencies.
* use a proper type for plugin dependencies
* rebase fixes
* message when cannot install
This allows external integrations ( btcpay docker fragments) to highlight specific plugins as recommended to be installed. Also moved the remote option to a config option instead of a url query param to avoid messy situations where users could get deceived with a generated url. The dockerfiles also have an additional csproj to build and the plugin dir was renamed correctly from extensions to plugins
Adds a warning to configure the e-mail server before "Requires a confirmation mail for registering" checkbox can be checked if e-mail server is not configured.
close#1889
* Remove QuadrigaCX references
Quadriga has been dead for years. I've removed the references to them and replaced them with a different Canadian exchange (ndax) for example.
The whole set of instructions could probably use an overhaul, but for now, at least let's get rid of Gerry's presence.
* Remove Quadriga from tests too
Co-authored-by: Kukks <evilkukka@gmail.com>
