Support Embedded Structs

[gbdubs]

If you have a parent struct that has an embedded child struct, the fields of the child struct will not get their SOQL fields marshaled.

type Parent struct {
   Child
}
type Child struct {
   Field string `soql:"selectColumn,fieldName=My_Field__c"`
}

Marshalling a query including the parent will omit Field despite it being a directly accessible member of Parent. I believe this is incongruous with how JSON serialization works in Golang.

I'd be happy to pick this up as an external contribution with a few pointers!