Nextcloud integration should use language as defined in cloud settings

[akhil1508]

Is your feature request related to a problem? Please describe.

• There is a separate language setting in snappymail when I use it inside a nextcloud setup
• This does not make sense to have two separate language settings when I want it to "integrate" with my cloud

Describe the solution you'd like

• Use language setting from cloud
• If the cloud language is not available in snappymail, fall back to "en"

Additional context

[the-djmaze]

It is now here:

snappymail/plugins/nextcloud/index.php

Lines 248 to 257 in ddc953f

	public function FilterLanguage($bAdmin, &$sLanguage) : void
	{
	if (!\RainLoop\Api::Config()->Get('webmail', 'allow_languages_on_settings', true)) {
	$sLanguage = \RainLoop\Api::Actions()->ValidateLanguage(
	\OC::$server->getL10N('core')->getLocaleCode(),
	$sLanguage,
	$bAdmin
	);
	}
	}