added a docker dev environment

Signed-off-by: Jan Friedli <jan.friedli@immerda.ch>

utils.py

@@ -0,0 +1,22 @@
+import os
+import hashlib
+
+
+def get_allow_origin_header_value():
+    return os.environ.get('MAT2_ALLOW_ORIGIN_WHITELIST', '*').split(" ")
+
+
+def hash_file(filepath: str) -> str:
+    sha256 = hashlib.sha256()
+    with open(filepath, 'rb') as f:
+        while True:
+            data = f.read(65536)  # read the file by chunk of 64k
+            if not data:
+                break
+            sha256.update(data)
+    return sha256.hexdigest()
+
+
+def check_upload_folder(upload_folder):
+    if not os.path.exists(upload_folder):
+        os.mkdir(upload_folder)