bug: don't call NumField on anything other than a struct

[zsiec]

This patch fixes a panic when the request object is a slice rather than a struct or pointer to a struct.

Example panic-ing method: https://github.com/bitmovin/bitmovin-api-sdk-go/blob/master/encoding/encoding_encodings_streams_filters_api.go#L28

NumField is called without checking if the value is a struct and documentation states NumField returns the number of fields in the struct v, It panics if v's Kind is not Struct. (https://github.com/golang/go/blob/master/src/reflect/value.go#L1345)

[zsiec]

I've taken a basic approach to fix this here. Depending on your needs, you may choose to loop through the slice and try to enrich structs that have props of type time.Time or *time.Time inside the slice, or even introduce some recursion if the slice is holding slices.

[CLAassistant]

All committers have signed the CLA.