feat: add currencies XAG and XAU (#535)

* Added currencies XAG and XAU to currency.ts

I added XAG and XAU for myself and others who prefer to measure value with something of substance.

Review the ISO 4217 standard to view a full list of official currency codes including the ones I have added.

https://www.iso.org/iso-4217-currency-codes.html
https://en.wikipedia.org/wiki/ISO_4217

Example:
https://www.xe.com/currencyconverter/convert/?Amount=100&From=XAG&To=USD

API for exchange rates:
https://openexchangerates.org/

* Added field values xag and xau to group.go

* Update group.go

backend/internal/data/ent/group/group.go

@@ -160,6 +160,8 @@ const (
 	CurrencyThb Currency = "thb"
 	CurrencyTry Currency = "try"
 	CurrencyUsd Currency = "usd"
+	CurrencyXag Currency = "xag"
+	CurrencyXau Currency = "xau"
 	CurrencyZar Currency = "zar"
 )
 
@@ -170,7 +172,7 @@ func (c Currency) String() string {
 // CurrencyValidator is a validator for the "currency" field enum values. It is called by the builders before save.
 func CurrencyValidator(c Currency) error {
 	switch c {
-	case CurrencyAed, CurrencyAud, CurrencyBgn, CurrencyBrl, CurrencyCad, CurrencyChf, CurrencyCny, CurrencyCzk, CurrencyDkk, CurrencyEur, CurrencyGbp, CurrencyHkd, CurrencyIdr, CurrencyInr, CurrencyJpy, CurrencyKrw, CurrencyMxn, CurrencyNok, CurrencyNzd, CurrencyPln, CurrencyRmb, CurrencyRon, CurrencyRub, CurrencySar, CurrencySek, CurrencySgd, CurrencyThb, CurrencyTry, CurrencyUsd, CurrencyZar:
+	case CurrencyAed, CurrencyAud, CurrencyBgn, CurrencyBrl, CurrencyCad, CurrencyChf, CurrencyCny, CurrencyCzk, CurrencyDkk, CurrencyEur, CurrencyGbp, CurrencyHkd, CurrencyIdr, CurrencyInr, CurrencyJpy, CurrencyKrw, CurrencyMxn, CurrencyNok, CurrencyNzd, CurrencyPln, CurrencyRmb, CurrencyRon, CurrencyRub, CurrencySar, CurrencySek, CurrencySgd, CurrencyThb, CurrencyTry, CurrencyUsd, CurrencyXag, CurrencyXau, CurrencyZar:
 		return nil
 	default:
 		return fmt.Errorf("group: invalid enum value for currency field: %q", c)

backend/internal/data/ent/schema/group.go

@@ -58,6 +58,8 @@ func (Group) Fields() []ent.Field {
 				"thb",
 				"try",
 				"usd",
+				"xag",
+				"xau",
 				"zar",
 			),
 	}

frontend/lib/data/currency.ts

@@ -27,6 +27,8 @@ export type Codes =
   | "THB"
   | "TRY"
   | "USD"
+  | "XAG"
+  | "XAU"
   | "ZAR";
 
 export type Currency = {
@@ -65,5 +67,7 @@ export const currencies: Currency[] = [
   { code: "THB", local: "Thailand", symbol: "฿", name: "Thai Baht" },
   { code: "TRY", local: "Turkey", symbol: "₺", name: "Turkish Lira" },
   { code: "USD", local: "United States", symbol: "$", name: "United States Dollar" },
+  { code: "XAG", local: "Global", symbol: "XAG", name: "Silver Troy Ounce" },
+  { code: "XAU", local: "Global", symbol: "XAU", name: "Gold Troy Ounce" },
   { code: "ZAR", local: "South Africa", symbol: "R", name: "South African Rand" },
 ];