smscalls: make checking for keys stricter

[purarue]

sort of reverts #287, but also makes some other improvements

this allows us to remove some of the Optional's to
make downstream consumers easier to write. However,
this keeps the return type as a Res (result, with errors),
so downstream consumers will have to handle those incase
the schema ever changes (highly unlikely)

also added the 'call_type/message_type' with a comment
there describing the values

I left 'who' Optional I believe it actually should be -
its very possible for there to be no contact name, added
a check incase its '(Unknown)' which is what my phone
sets it to

[purarue]

I left call_type/message_type an integer, could make it an Enum (but not a huge fan of pythons enum) or a Literal if you'd prefer

[karlicoss]

awesome, thanks! Yeah same, not really a fan of python enums