MAJOR: solves problem related to ELABFTW_API_URL variable

if no value was specified for such variable (or .env was missing)
EAU would be set to None and get stuck in a prompt loop

solved by turning EAU into a required variable in APIHandler
(and editing a lot of code through all of src/)

src/APIHandler.py

@@ -23,11 +23,11 @@ class APIHandler:
     # TO-DO: remove static url.
     def __init__(self, api_key="", ELABFTW_API_URL=None):
         """Init method, api_key suggested but not required (empty by default)."""
-        if not ELABFTW_API_URL:
-            load_dotenv()
-            ELABFTW_API_URL = os.getenv("ELABFTW_API_URL") or input(
-                "Enter a valid eLabFTW API URL (ends with '/api/v2)': "
-            )
+        # if not ELABFTW_API_URL:
+        #    load_dotenv()
+        #    ELABFTW_API_URL = os.getenv("ELABFTW_API_URL") or input(
+        #        "Enter a valid eLabFTW API URL (ends with '/api/v2)': "
+        #    )
         self.api_key = api_key
         self.auth = {"Authorization": api_key}
         self.content = {"Content-Type": "application/json"}