chore: utility to handle string IDs (#884)

All current resources use string IDs, but they are ints in hcloud-go.
This util helps convert between them.

Will be used by #817

internal/util/resourceutil/id.go

@@ -0,0 +1,35 @@
+package resourceutil
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+
+	"github.com/hashicorp/terraform-plugin-framework/diag"
+	"github.com/hashicorp/terraform-plugin-framework/path"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+)
+
+func ParseID(value types.String) (int, diag.Diagnostics) {
+	var diagnostics diag.Diagnostics
+	id, err := strconv.ParseInt(value.ValueString(), 10, 64)
+	if err != nil {
+		diagnostics.AddAttributeError(
+			path.Root("id"),
+			"Could not parse resource ID",
+			err.Error(),
+		)
+		return 0, diagnostics
+	}
+	if id > math.MaxInt32 && strconv.IntSize == 32 {
+		diagnostics.AddAttributeError(
+			path.Root("id"),
+			"ID is larger than your system supports.",
+			"The current version of the provider has problems with IDs > 32bit on 32 bit systems. If possible, switch to a 64 bit system for now. See https://github.com/hetznercloud/hcloud-go/issues/263")
+	}
+	return int(id), diagnostics
+}
+
+func IDStringValue(value int) types.String {
+	return types.StringValue(fmt.Sprintf("%d", value))
+}