Don't update expires in MemoryPersistDriver.set if it is nil (#562)

Author: adam-fowler

Sources/Hummingbird/Storage/MemoryPersistDriver.swift

@@ -29,7 +29,8 @@ public actor MemoryPersistDriver<C: Clock>: PersistDriver where C.Duration == Du
     }
 
     public func set(key: String, value: some Codable & Sendable, expires: Duration?) async throws {
-        self.values[key] = .init(value: value, expires: expires.map { self.clock.now.advanced(by: $0) })
+        let expiresAt = expires.map { self.clock.now.advanced(by: $0) } ?? self.values[key]?.expires
+        self.values[key] = .init(value: value, expires: expiresAt)
     }
 
     public func get<Object: Codable & Sendable>(key: String, as: Object.Type) async throws -> Object? {

Sources/Hummingbird/Storage/PersistDriver.swift

@@ -31,7 +31,8 @@ public protocol PersistDriver: Service {
     /// - Parameters:
     ///   - key: Key to store value against
     ///   - value: Codable value to store
-    ///   - expires: If non-nil defines time that value will expire
+    ///   - expires: If non-nil defines time that value will expire in. If nil and value already exists
+    ///      and it already has an expiration time then original expiration time should be conserved.
     func set<Object: Codable & Sendable>(key: String, value: Object, expires: Duration?) async throws
 
     /// get value for key