Fix set_license with utf-8 chars

Using the json encoder manage for us the encoding/decoding on sender
receiver.

[ch63983]

Author: adescamps

dataikuapi/dssclient.py

@@ -999,7 +999,7 @@ def set_license(self, license):
         :return: None
         """
         self._perform_empty(
-            "POST", "/admin/licensing/license", raw_body=license)
+            "POST", "/admin/licensing/license", body=json.loads(license))
 
 
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