[Feat] Add FirestoreDocumentSupportable protocol and declare isDocumentExsts(endpoint:) method

Author: SHcommit

Sources/SHFirestoreService/FirestoreDocumentSupportable.swift

@@ -0,0 +1,13 @@
+//
+//  FirestoreDocumentSupportable.swift
+//  
+//
+//  Created by 양승현 on 5/16/24.
+//
+
+import Combine
+import Foundation
+
+public protocol FirestoreDocumentSupportable {
+  func isDocumentExists(endpoint: any FirestoreEndopintable) -> AnyPublisher<Bool, FirestoreServiceError>
+}