Correctly join URLs like a pro instead of stiching them together

cgi-bin/form.py

@@ -1,17 +1,17 @@
 #!/usr/bin/env python
 
 import base64
-import io
 import cgi
 import collections
 from collections.abc import Mapping
 import hmac
-import mimetypes
-import re
-import os
-import secrets
 import json
+import mimetypes
+import os
+import re
+import secrets
 from typing import Any, Optional, overload
+from urllib.parse import urljoin
 
 import itsdangerous
 import requests
@@ -303,7 +303,7 @@ ticket_details["Kontaktformular"] = form_name
 # testing).
 form_group = os.environ.get("ZAMMAD_GROUP", "") or form_group
 
-ZAMMAD_URL = os.environ.get("ZAMMAD_URL", "").rstrip("/")
+ZAMMAD_URL = os.environ.get("ZAMMAD_URL", "")
 ZAMMAD_TOKEN = os.environ.get("ZAMMAD_TOKEN", "")
 session.headers.update(Authorization=f"Token token={ZAMMAD_TOKEN}")
 
@@ -315,7 +315,7 @@ try:
 	# [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",
+		urljoin(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
@@ -335,7 +335,7 @@ try:
 
 	# Add the actual ticket to the system.
 	response = session.post(
-		f"{ZAMMAD_URL}/api/v1/tickets",
+		urljoin(ZAMMAD_URL, "api/v1/tickets"),
 		headers={
 			"X-On-Behalf-Of": contact_email,
 		},
@@ -364,7 +364,7 @@ try:
 	# Add a second article to the ticket that contains all the other information
 	# from the contact form.
 	response = session.post(
-		f"{ZAMMAD_URL}/api/v1/ticket_articles",
+		urljoin(ZAMMAD_URL, "api/v1/ticket_articles"),
 		json=dict(
 			ticket_id=ticket_id,
 			type="note",
@@ -379,7 +379,7 @@ try:
 
 	# Add a tag to the ticket, denoting which contact form it came from.
 	response = session.post(
-		f"{ZAMMAD_URL}/api/v1/tags/add",
+		urljoin(ZAMMAD_URL, "api/v1/tags/add"),
 		json=dict(
 			object="Ticket",
 			o_id=ticket_id,