fix: pypi package should not pin dependencies precisely (#670)

* fix: pypi package should not pin dependencies precisely

Signed-off-by: Nicolas Höning <nicolas@seita.nl>

* add docstring to explain why we use .in

---------

Signed-off-by: Nicolas Höning <nicolas@seita.nl>

setup.py

@@ -2,8 +2,15 @@
 
 
 def load_requirements(use_case):
+    """
+    Loading range requirements.
+    Packaging should be used for installing the package into existing stacks.
+    We therefore read the .in file for the use case.
+    .txt files include the exact pins, and are useful for deployments with
+    exactly comparable environments.
+    """
     reqs = []
-    with open("requirements/%s.txt" % use_case, "r") as f:
+    with open("requirements/%s.in" % use_case, "r") as f:
         reqs = [
             req
             for req in f.read().splitlines()