fix(API): filter null values of requrest structs

Some servers, like youtube, reject null values possibly thanks to
the reliance on parts. Now we are filtering them (in a very inefficient,
but working way), which seems to be fine with the servers.

Effectively, we seem to be able now to upload videos ... .

More testing required !

etc/api/type-api.yaml

@@ -27,3 +27,4 @@ cargo:
     - url = "*"
     - serde = ">= 0.3.0"
     - serde_macros = "*"
+    - json-tools = "*"

etc/api/type-cli.yaml

@@ -31,4 +31,3 @@ cargo:
     - serde = ">= 0.3.0"
     - serde_macros = "*"
     - clap = "*"
-    - json-tools = "*"