Resolve warnings when not using the resulting catalog

Author: joshheald

Modules/Sources/Yosemite/Tools/POS/POSCatalogIncrementalSyncService.swift

@@ -14,7 +14,10 @@ public protocol POSCatalogIncrementalSyncServiceProtocol {
     ///   - siteID: The site ID to sync catalog for.
     ///   - lastFullSyncDate: The date of the last full sync to use if no incremental sync date exists.
     /// - Returns: The synced catalog containing updated products and variations
-    func startIncrementalSync(for siteID: Int64, lastFullSyncDate: Date, lastIncrementalSyncDate: Date?) async throws -> POSCatalog
+    @discardableResult
+    func startIncrementalSync(for siteID: Int64,
+                              lastFullSyncDate: Date,
+                              lastIncrementalSyncDate: Date?) async throws -> POSCatalog
 }
 
 // TODO - remove the periphery ignore comment when the service is integrated with POS.
@@ -53,7 +56,7 @@ public final class POSCatalogIncrementalSyncService: POSCatalogIncrementalSyncSe
     }
 
     // MARK: - Protocol Conformance
-
+    @discardableResult
     public func startIncrementalSync(for siteID: Int64, lastFullSyncDate: Date, lastIncrementalSyncDate: Date?) async throws -> POSCatalog {
         let modifiedAfter = latestSyncDate(fullSyncDate: lastFullSyncDate, incrementalSyncDate: lastIncrementalSyncDate)
 

Modules/Tests/YosemiteTests/Mocks/MockPOSCatalogIncrementalSyncService.swift

@@ -13,6 +13,7 @@ final class MockPOSCatalogIncrementalSyncService: POSCatalogIncrementalSyncServi
     private var shouldBlockSync = false
     private var syncBlockedContinuations: [CheckedContinuation<Void, Never>] = []
 
+    @discardableResult
     func startIncrementalSync(for siteID: Int64, lastFullSyncDate: Date, lastIncrementalSyncDate: Date?) async throws -> POSCatalog {
         startIncrementalSyncCallCount += 1
         lastSyncSiteID = siteID