core: make binary envelope behave like bytes type object for serialization and internal API usage.

We would need to unpack it otherwise manually

vcsserver/base.py

@@ -140,3 +140,39 b' class BinaryEnvelope(object):'
     def __init__(self, value, bin_type=True):
         self.value = value
         self.bin_type = bin_type
+
+    def __len__(self):
+        return len(self.value)
+
+    def __getitem__(self, index):
+        return self.value[index]
+
+    def __iter__(self):
+        return iter(self.value)
+
+    def __str__(self):
+        return str(self.value)
+
+    def __repr__(self):
+        return repr(self.value)
+
+    def __eq__(self, other):
+        if isinstance(other, BinaryEnvelope):
+            return self.value == other.value
+        return False
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __add__(self, other):
+        if isinstance(other, BinaryEnvelope):
+            return BinaryEnvelope(self.value + other.value)
+        raise TypeError(f"unsupported operand type(s) for +: 'BinaryEnvelope' and '{type(other)}'")
+
+    def __radd__(self, other):
+        if isinstance(other, BinaryEnvelope):
+            return BinaryEnvelope(other.value + self.value)
+        raise TypeError(f"unsupported operand type(s) for +: '{type(other)}' and 'BinaryEnvelope'")
+
+
+