Generate UnmarshalJSON to handle emptyStringInt types

This commit changes the code generator to generate a `UnmarshalJSON` for each
struct, so that if unmarshalled it properly handles UniFis varying integer values
via the `emptyStringInt` type.

Structs not including a field of `int` type will still have the function generated,
but it will effectively do nothing.

Fixes #18

unifi/account.go

@@ -3,33 +3,8 @@ package unifi
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 )
 
-func (dst *Account) UnmarshalJSON(b []byte) error {
-	type Alias Account
-	aux := &struct {
-		TunnelType       emptyStringInt `json:"tunnel_type"`
-		TunnelMediumType emptyStringInt `json:"tunnel_medium_type"`
-		VLAN             emptyStringInt `json:"vlan"`
-
-		*Alias
-	}{
-		Alias: (*Alias)(dst),
-	}
-
-	err := json.Unmarshal(b, &aux)
-	if err != nil {
-		return fmt.Errorf("unable to unmarshal alias: %w", err)
-	}
-
-	dst.TunnelType = int(aux.TunnelType)
-	dst.TunnelMediumType = int(aux.TunnelMediumType)
-	dst.VLAN = int(aux.VLAN)
-
-	return nil
-}
-
 func (dst *Account) MarshalJSON() ([]byte, error) {
 	type Alias Account
 	aux := &struct {