Fixed: Mis-classification of releases as being Czech (#3378)

After the changes from PR #2948, the regex was too eager to match any
substring contain "SK", such as in "MASK". Fix by requiring word
separation around it, as was already the case with the "CZ" token.

src/NzbDrone.Core.Test/ParserTests/LanguageParserFixture.cs

@@ -49,6 +49,7 @@ namespace NzbDrone.Core.Test.ParserTests
         [TestCase("The Danish Girl 2015", Language.English)]
         [TestCase("Nocturnal Animals (2016) MULTi VFQ English [1080p] BluRay x264-PopHD", Language.English, Language.French)]
         [TestCase("Wonder.Woman.2017.720p.BluRay.DD5.1.x264-TayTO.CZ-FTU", Language.Czech)]
+        [TestCase("Fantastic.Beasts.The.Crimes.Of.Grindelwald.2018.2160p.WEBRip.x265.10bit.HDR.DD5.1-GASMASK", Language.English)]
         public void should_parse_language(string postTitle, params Language[] languages)
         {
             var movieInfo = Parser.Parser.ParseMovieTitle(postTitle, true);

src/NzbDrone.Core/Parser/LanguageParser.cs

@@ -13,7 +13,7 @@ namespace NzbDrone.Core.Parser
     {
         private static readonly Logger Logger = NzbDroneLogger.GetLogger(typeof(LanguageParser));
 
-        private static readonly Regex LanguageRegex = new Regex(@"(?:\W|_)(?<italian>\b(?:ita|italian)\b)|(?<german>german\b|videomann)|(?<flemish>flemish)|(?<greek>greek)|(?<french>(?:\W|_)(?:FR|VOSTFR|VO|VFF|VFQ|VF2|TRUEFRENCH)(?:\W|_))|(?<russian>\brus\b)|(?<dutch>nl\W?subs?)|(?<hungarian>\b(?:HUNDUB|HUN)\b)|(?<hebrew>\bHebDub\b)|(?<czech>\bCZ|SK\b)",
+        private static readonly Regex LanguageRegex = new Regex(@"(?:\W|_)(?<italian>\b(?:ita|italian)\b)|(?<german>german\b|videomann)|(?<flemish>flemish)|(?<greek>greek)|(?<french>(?:\W|_)(?:FR|VOSTFR|VO|VFF|VFQ|VF2|TRUEFRENCH)(?:\W|_))|(?<russian>\brus\b)|(?<dutch>nl\W?subs?)|(?<hungarian>\b(?:HUNDUB|HUN)\b)|(?<hebrew>\bHebDub\b)|(?<czech>\b(?:CZ|SK)\b)",
                                                                 RegexOptions.IgnoreCase | RegexOptions.Compiled);
 
         private static readonly Regex SubtitleLanguageRegex = new Regex(".+?[-_. ](?<iso_code>[a-z]{2,3})$", RegexOptions.Compiled | RegexOptions.IgnoreCase);