Explicitly create users in Zammad before using them

Closes #40. Closes #141. For some reason, Zammad behaves differently when
the corresponding user doesn't exit yet. This also allows us to
explicitly set a name for users (at least for new ones).

cgi-bin/form.py

@@ -158,7 +158,10 @@ def get_form_value(
 		return (value_object.filename or "upload"), value_object.file.read()
 	else:
 		try:
-			return cast(form.getfirst(name))
+			result = cast(form.getfirst(name))
+			if isinstance(result, str):
+				result = result.strip()
+			return result
 		except (TypeError, ValueError):
 			fail("400 Bad Request", f"Invalid value for field: {name}")
 
@@ -187,6 +190,7 @@ if not isinstance(hcaptcha_data, Mapping) or not hcaptcha_data.get("success", Fa
 # Extract all the actually provided form data. This is different from form to
 # form (see the match block below).
 contact_name = get_form_value("contactname")
+contact_names = contact_name.split(" ")
 
 contact_email = get_form_value("contactemail")
 if not EMAIL_REGEX.fullmatch(contact_email):
@@ -289,13 +293,41 @@ ZAMMAD_TOKEN = os.environ.get("ZAMMAD_TOKEN", "")
 session.headers.update(Authorization=f"Token token={ZAMMAD_TOKEN}")
 
 try:
+	# Create a new user for the client. For some reason, using "guess:{email}" as the
+	# customer_id when creating the ticket doesn't really work, as described in the
+	# Zammad documentation [1]. Instead, we sometimes need to explictily create the
+	# user beforehand. See this discussion [2] for more details.
+	# [1]: https://docs.zammad.org/en/latest/api/ticket/index.html#create
+	# [2]: https://codeberg.org/angestoepselt/homepage/issues/141
+	response = session.post(
+		f"{ZAMMAD_URL}/api/v1/users",
+		json=dict(
+			# Yes, yes... This goes against pretty much all best practices for parsing
+			# names. But: it's only internal and we save the name verbatim again below
+			# so we're going to go ahead and do it anyway.
+			firstname=" ".join(contact_names[:-1]) if len(contact_names) >= 2 else "?",
+			lastname=contact_names[-1],
+			email=contact_email,
+		)
+	)
+	if response.status_code == 422:
+		# This email address is already in use by another user.
+		customer_id = f"guess:{contact_email}"
+	else:
+		response.raise_for_status()
+		customer_id = response.json()["id"]
+		assert isinstance(customer_id, (str, int))
+
 	# Add the actual ticket to the system.
 	response = session.post(
 		f"{ZAMMAD_URL}/api/v1/tickets",
+		headers={
+			"X-On-Behalf-Of": contact_email,
+		},
 		json=dict(
 			title=f"Kontaktformular {contact_name} – {form_name}",
 			group=form_group,
-			customer_id=f"guess:{contact_email}",
+			customer_id=customer_id,
 			article=dict(
 				type="web",
 				internal=True,