fun part(name: String, part: Any): PartBuilder
Adds a part to this builder, allowing for further header customization with the returned PartBuilder.
name - the name of the part to add (may not be empty)
Return
a builder that allows for further header customization
fun part(name: String, part: Any, @Nullable contentType: MediaType): PartBuilder
Adds a part to this builder, allowing for further header customization with the returned PartBuilder.
name - the name of the part to add (may not be empty)
contentType - the Content-Type header for the part (may be null)
Return
a builder that allows for further header customization