Bug fix - email processing could be run now from API (#2613)

### What problem does this PR solve?

If .eml file is uploaded, there is always General method chosen for
email processing, even if parsing_method is defined in the request. This
change solves this issue.

### Type of change

- [X] Bug Fix (non-breaking change which fixes an issue)

Co-authored-by: Adam Kobus <adam.kobus@gitlab.eleader.biz>

api/apps/api_app.py

             doc["parser_id"] = ParserType.AUDIO.value
         if re.search(r"\.(ppt|pptx|pages)$", filename):
             doc["parser_id"] = ParserType.PRESENTATION.value
+        if re.search(r"\.(eml)$", filename):
+            doc["parser_id"] = ParserType.EMAIL.value
 
         doc_result = DocumentService.insert(doc)
         FileService.add_file_from_kb(doc, kb_folder["id"], kb.tenant_id)