Add a config object

- add the following file:
  + src/urban_meal_delivery/_config.py
- a config module is created holding two sets of configurations:
  + production => against the real database
  + testing => against a database with test data
- the module is "protected" (i.e., underscore) and imported at the
  top level via a proxy-like object `config` that detects in which of
  the two environments the package is being run

setup.cfg

@@ -109,6 +109,11 @@ per-file-ignores =
         WPS213,
         # No overuse of string constants (e.g., '--version').
         WPS226,
+    src/urban_meal_delivery/_config.py:
+        # Allow upper case class variables within classes.
+        WPS115,
+        # Numbers are normal in config files.
+        WPS432,
     tests/*.py:
         # Type annotations are not strictly enforced.
         ANN0, ANN2,
@@ -135,10 +140,10 @@ show-source = true
 # wemake-python-styleguide's settings
 # ===================================
 allowed-domain-names =
+    obj,
     param,
     result,
     value,
-min-name-length = 3
 max-name-length = 40
 # darglint
 strictness = long
@@ -186,7 +191,13 @@ single_line_exclusions = typing
 [mypy]
 cache_dir = .cache/mypy
 
-[mypy-nox.*,packaging,pytest]
+[mypy-dotenv]
+ignore_missing_imports = true
+[mypy-nox.*]
+ignore_missing_imports = true
+[mypy-packaging]
+ignore_missing_imports = true
+[mypy-pytest]
 ignore_missing_imports = true