feat(config): add AppConfig with property "dsn" for sentry initialization

src/repdav/config.py

-import logging
 import os
-from .errors import EnvNotSetError
 
+from .errors import EnvNotSetError
 
-_logger = logging.getLogger(__name__)
+# TODO: remove "tg_auth_wsdl", "tg_auth_address", "tg_nav_address"
 
 
 def lookup_env_name(internal_name: str) -> str:
     mapping = {
-        "_auth_wsdl" : "tg_auth_wsdl",
-        "_auth_address" : "tg_auth_address",
-        "_nav_address" : "tg_nav_address",
-        "_host" : "tg_host",
+        "_auth_wsdl": "tg_auth_wsdl",
+        "_auth_address": "tg_auth_address",
+        "_dsn": "sentry_dsn",
+        "_host": "tg_host",
+        "_nav_address": "tg_nav_address",
     }
     return mapping[internal_name]
 
+
 # TODO check for trailing "/", add if missing!
+# TODO check URLs for validity
+
+class AppConfig:
+    # TODO: configure the app according to the set environment (i.e. prod or dev)
+    def __init__(self) -> None:
+        self._dsn = os.getenv(lookup_env_name("_dsn"))
+
+    @property
+    def dsn(self) -> str:
+        return self._dsn
+
+
 class TextgridConfig:
-    def __init__(self):
+    def __init__(self) -> None:
         self._auth_wsdl = os.getenv(lookup_env_name("_auth_wsdl"))
         self._auth_address = os.getenv(lookup_env_name("_auth_address"))
-        self._nav_address =  os.getenv(lookup_env_name("_nav_address"))
-        self._host =  os.getenv(lookup_env_name("_host"))
+        self._nav_address = os.getenv(lookup_env_name("_nav_address"))
+        self._host = os.getenv(lookup_env_name("_host"))
 
     @property
-    def auth_wsdl(self):
+    def auth_wsdl(self) -> str:
         if self._auth_wsdl:
-            _logger.debug(self._auth_wsdl)
             return self._auth_wsdl
         raise EnvNotSetError(lookup_env_name("_auth_wsdl"))
 
     @property
-    def auth_address(self):
+    def auth_address(self) -> str:
         if self._auth_address:
             return self._auth_address
         raise EnvNotSetError(lookup_env_name("_auth_address"))
 
     @property
-    def nav_address(self):
+    def nav_address(self) -> str:
         if self._nav_address:
             return self._nav_address
         raise EnvNotSetError(lookup_env_name("_nav_address"))
 
     @property
-    def host(self):
+    def host(self) -> str:
         if self._host:
             return self._host
         raise EnvNotSetError(lookup_env_name("_host"))