Backport remaining v2 changes to phase4

data/fields.py

@@ -0,0 +1,38 @@
+import base64
+import resumablehashlib
+import json
+
+from peewee import TextField
+
+
+class ResumableSHAField(TextField):
+  def db_value(self, value):
+    sha_state = value.state()
+
+    # One of the fields is a byte string, let's base64 encode it to make sure
+    # we can store and fetch it regardless of default collocation.
+    sha_state[3] = base64.b64encode(sha_state[3])
+
+    return json.dumps(sha_state)
+
+  def python_value(self, value):
+    to_resume = resumablehashlib.sha256()
+    if value is None:
+      return to_resume
+
+    sha_state = json.loads(value)
+
+    # We need to base64 decode the data bytestring.
+    sha_state[3] = base64.b64decode(sha_state[3])
+    to_resume.set_state(sha_state)
+    return to_resume
+
+
+class JSONField(TextField):
+  def db_value(self, value):
+    return json.dumps(value)
+
+  def python_value(self, value):
+    if value is None or value == "":
+      return {}
+    return json.loads(value)