Use specific types for all fields on machine (no datatypes.json)

This commit removes the need for datatypes.JSON and makes the code a bit
cleaner by allowing us to use proper types throughout the code when it
comes to hostinfo and other datatypes on the machine object.

This allows us to remove alot of unmarshal/marshal operations and remove
a lot of obsolete error checks.

This following commits will clean away a lot of untyped data and
uneccessary error checks.

db.go

@@ -1,13 +1,18 @@
 package headscale
 
 import (
+	"database/sql/driver"
+	"encoding/json"
 	"errors"
+	"fmt"
 	"time"
 
 	"github.com/glebarez/sqlite"
 	"gorm.io/driver/postgres"
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
+	"inet.af/netaddr"
+	"tailscale.com/tailcfg"
 )
 
 const (
@@ -141,3 +146,74 @@ func (h *Headscale) setValue(key string, value string) error {
 
 	return nil
 }
+
+// This is a "wrapper" type around tailscales
+// Hostinfo to allow us to add database "serialization"
+// methods. This allows us to use a typed values throughout
+// the code and not have to marshal/unmarshal and error
+// check all over the code.
+type HostInfo tailcfg.Hostinfo
+
+func (hi *HostInfo) Scan(destination interface{}) error {
+	switch value := destination.(type) {
+	case []byte:
+		return json.Unmarshal(value, hi)
+
+	case string:
+		return json.Unmarshal([]byte(value), hi)
+
+	default:
+		return fmt.Errorf("%w: unexpected data type %T", errMachineAddressesInvalid, destination)
+	}
+}
+
+// Value return json value, implement driver.Valuer interface.
+func (hi HostInfo) Value() (driver.Value, error) {
+	bytes, err := json.Marshal(hi)
+
+	return string(bytes), err
+}
+
+type IPPrefixes []netaddr.IPPrefix
+
+func (i *IPPrefixes) Scan(destination interface{}) error {
+	switch value := destination.(type) {
+	case []byte:
+		return json.Unmarshal(value, i)
+
+	case string:
+		return json.Unmarshal([]byte(value), i)
+
+	default:
+		return fmt.Errorf("%w: unexpected data type %T", errMachineAddressesInvalid, destination)
+	}
+}
+
+// Value return json value, implement driver.Valuer interface.
+func (i IPPrefixes) Value() (driver.Value, error) {
+	bytes, err := json.Marshal(i)
+
+	return string(bytes), err
+}
+
+type StringList []string
+
+func (i *StringList) Scan(destination interface{}) error {
+	switch value := destination.(type) {
+	case []byte:
+		return json.Unmarshal(value, i)
+
+	case string:
+		return json.Unmarshal([]byte(value), i)
+
+	default:
+		return fmt.Errorf("%w: unexpected data type %T", errMachineAddressesInvalid, destination)
+	}
+}
+
+// Value return json value, implement driver.Valuer interface.
+func (i StringList) Value() (driver.Value, error) {
+	bytes, err := json.Marshal(i)
+
+	return string(bytes), err
+}