Fix languages field definition, adjust test and update readme (#87)

* fix languages field definition, adjust test and update readme

* Rename

---------

Co-authored-by: Raphael Michel <michel@rami.io>

Author: kuhntob

README.rst

@@ -66,7 +66,7 @@ Generating::
     doc.header.type_code = "380"
     doc.header.name = "RECHNUNG"
     doc.header.issue_date_time = date.today()
-    doc.header.languages.add("de")
+    doc.header.language = "ger"
 
     note = IncludedNote()
     note.content.add("Test Node 1")

drafthorse/models/document.py

@@ -80,7 +80,7 @@ class Header(Element):
         profile=EXTENDED,
         _d="Indikator Original/Kopie",
     )
-    languages: StringContainer = MultiStringField(
+    language = StringField(
         NS_RAM, "LanguageID", required=False, profile=EXTENDED
     )
     notes: Container = MultiField(IncludedNote)

tests/conftest.py

@@ -20,7 +20,7 @@ def invoice_document(request):
     doc.header.type_code = request.param
     doc.header.name = "RECHNUNG"
     doc.header.issue_date_time = date.today()
-    doc.header.languages.add("de")
+    doc.header.language = "ger"
 
     doc.header.notes.add(IncludedNote(content="Test Node 1"))