(converter) Refactor content type check in PlainTextDocumentProcessorPlugin

The method `isApplicable` in the `PlainTextDocumentProcessorPlugin` was refactored to handle a wider range of content types beyond merely "text/plain". It now also handles any content type that starts with "text/plain;", to accomodate contentTypes that append a charset as well.

code/processes/converting-process/src/main/java/nu/marginalia/converting/processor/plugin/PlainTextDocumentProcessorPlugin.java

@@ -54,7 +54,14 @@ public class PlainTextDocumentProcessorPlugin extends AbstractDocumentProcessorP
 
     @Override
     public boolean isApplicable(CrawledDocument doc) {
-        return doc.contentType.equalsIgnoreCase("text/plain");
+        String contentType = doc.contentType.toLowerCase();
+
+        if (contentType.equals("text/plain"))
+            return true;
+        if (contentType.startsWith("text/plain;")) // charset=blabla
+            return true;
+
+        return false;
     }
 
     @Override