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/swift/BreezSDKExamples/Sources/Metadata.swift

@@ -0,0 +1,76 @@
+//
+//  Metadata.swift
+//  
+//
+//
+
+import Foundation
+import BreezSDK
+
+func SetPaymentMetadata(sdk: BlockingBreezServices) throws {
+    // ANCHOR: set-payment-metadata
+    try sdk.setPaymentMetadata(hash: "target-payment-hash", metadata: #"{"myCustomValue":true}"#)    
+    // ANCHOR_END: set-payment-metadata
+}
+
+func FilterPaymentMetadata(sdk: BlockingBreezServices) -> [Payment]? {
+    // ANCHOR: filter-payment-metadata
+    let metadataFilters = [
+        MetadataFilter(
+            jsonPath: "myCustomValue",
+            jsonValue: "true"
+        )
+    ]
+
+    let payments = try? sdk.listPayments(
+        req: ListPaymentsRequest(
+            metadataFilters: metadataFilters
+        )
+    )
+    // ANCHOR_END: filter-payment-metadata
+
+    return payments
+}
+
+func FilterPaymentMetadataString(sdk: BlockingBreezServices) -> [Payment]? {
+    // ANCHOR: filter-payment-metadata-string
+    let metadataFilters = [
+        MetadataFilter(
+            jsonPath: "myCustomValue",
+            jsonValue: #""true""#
+        )
+    ]
+    // ANCHOR_END: filter-payment-metadata-string
+
+    return try? sdk.listPayments(
+        req: ListPaymentsRequest(
+            metadataFilters: metadataFilters
+        )
+    )
+}
+
+func FilterPaymentMetadataObject(sdk: BlockingBreezServices) -> [Payment]? {
+    // ANCHOR: filter-payment-metadata-object
+    // This will *NOT* work
+    var metadataFilters = [
+        MetadataFilter(
+            jsonPath: "myCustomValue",
+            jsonValue: #"[1, 2, 3]"#
+        )
+    ]
+
+    // Any of these will work
+    metadataFilters = [
+        MetadataFilter(
+            jsonPath: "myCustomValue",
+            jsonValue: #"[1,2,3]"#
+        )
+    ]
+    // ANCHOR_END: filter-payment-metadata-object
+
+    return try? sdk.listPayments(
+        req: ListPaymentsRequest(
+            metadataFilters: metadataFilters
+        )
+    )
+}