feat: adding docs for payment metadata (#124)

Co-authored-by: vacwmX <vacwm01@gmail.com>
Co-authored-by: ok300 <106775972+ok300@users.noreply.github.com>

snippets/go/metadata.go

@@ -0,0 +1,72 @@
+package example
+
+import (
+	"encoding/json"
+	"log"
+
+	"github.com/breez/breez-sdk-go/breez_sdk"
+)
+
+func SetPaymentMetadata() {
+	// ANCHOR: set-payment-metadata
+	sdk.SetPaymentMetadata("target-payment-hash", `{"myCustomValue":true}`)
+	// ANCHOR_END: set-payment-metadata
+}
+
+func FilterPaymentMetadata() {
+	// ANCHOR: filter-payment-metadata
+	metadataFilters := []breez_sdk.MetadataFilter{
+		{JsonPath: "myCustomValue", JsonValue: "true"},
+	}
+
+	payments, err := sdk.ListPayments(breez_sdk.ListPaymentsRequest{
+		MetadataFilters: &metadataFilters,
+	})
+
+	if err != nil {
+		// handle error
+	}
+	// ANCHOR_END: filter-payment-metadata
+	log.Printf("%#v", payments)
+}
+
+func FilterPaymentMetadataString() {
+	// ANCHOR: filter-payment-metadata-string
+	metadataFilters := []breez_sdk.MetadataFilter{
+		{JsonPath: "customerName", JsonValue: "\"Satoshi Nakamoto\""},
+	}
+
+	jsonValue, _ := json.Marshal("Satoshi Nakamoto")
+	metadataFilters = []breez_sdk.MetadataFilter{
+		{
+			JsonPath:  "customerName",
+			JsonValue: string(jsonValue),
+		},
+	}
+	// ANCHOR_END: filter-payment-metadata-string
+
+	sdk.ListPayments(breez_sdk.ListPaymentsRequest{
+		MetadataFilters: &metadataFilters,
+	})
+}
+
+func FilterPaymentMetadataObject() {
+	// ANCHOR: filter-payment-metadata-object
+	// This will *NOT* work
+	metadataFilters := []breez_sdk.MetadataFilter{
+		{JsonPath: "parent.nestedArray", JsonValue: "[1, 2, 3]"},
+	}
+
+	// Any of these will work
+	jsonValue, _ := json.Marshal([]int{1, 2, 3})
+
+	metadataFilters = []breez_sdk.MetadataFilter{
+		{JsonPath: "parent.nestedArray", JsonValue: "[1,2,3]"},
+		{JsonPath: "parent.nestedArray", JsonValue: string(jsonValue)},
+	}
+	// ANCHOR_END: filter-payment-metadata-object
+
+	sdk.ListPayments(breez_sdk.ListPaymentsRequest{
+		MetadataFilters: &metadataFilters,
+	})
+}