swift 5.2 -> 6.2.1, dependency upgrade, improved concurrency safety

Author: TopScrech

Package.swift

@@ -1,26 +1,26 @@
-// swift-tools-version:5.2
-// The swift-tools-version declares the minimum version of Swift required to build this package.
+// swift-tools-version:6.2.1
+// The swift-tools-version declares the minimum version of Swift required to build this package
 
 import PackageDescription
 
 let package = Package(
     name: "Smtp",
     platforms: [
-       .macOS(.v10_15)
+        .macOS(.v10_15)
     ],
     products: [
         // Products define the executables and libraries produced by a package, and make them visible to other packages.
         .library(name: "Smtp", targets: ["Smtp"])
     ],
     dependencies: [
-        // 💧 A server-side Swift web framework. 
-        .package(url: "https://github.com/vapor/vapor.git", .upToNextMajor(from: "4.0.1")),
-
-        // Event-driven network application framework for high performance protocol servers & clients, non-blocking.
-        .package(url: "https://github.com/apple/swift-nio.git", .upToNextMajor(from: "2.16.0")),
-
+        // 💧 A server-side Swift web framework
+        .package(url: "https://github.com/vapor/vapor.git", .upToNextMajor(from: "4.121.1")),
+        
+        // Event-driven network application framework for high performance protocol servers & clients, non-blocking
+        .package(url: "https://github.com/apple/swift-nio.git", .upToNextMajor(from: "2.93.0")),
+        
         // Bindings to OpenSSL-compatible libraries for TLS support in SwiftNIO
-        .package(url: "https://github.com/apple/swift-nio-ssl.git", .upToNextMajor(from: "2.7.1"))
+        .package(url: "https://github.com/apple/swift-nio-ssl.git", .upToNextMajor(from: "2.36.0"))
     ],
     targets: [
         .target(name: "Smtp", dependencies: [

Sources/Smtp/Models/HelloMethod.swift

@@ -4,7 +4,7 @@
 //  Licensed under the MIT License.
 //
 
-public enum HelloMethod: String {
+public enum HelloMethod: String, Sendable {
     case helo = "HELO"
     case ehlo = "EHLO"
 }

Sources/Smtp/Models/SignInMethod.swift

@@ -4,7 +4,7 @@
 //  Licensed under the MIT License.
 //
 
-public enum SignInMethod {
+public enum SignInMethod: Sendable {
     case anonymous
     case credentials(username: String, password: String)
 }

Sources/Smtp/SmtpSecure.swift

@@ -8,7 +8,7 @@ import Vapor
 import NIO
 import NIOSSL
 
-public enum SmtpSecureChannel {
+public enum SmtpSecureChannel: Sendable {
 
     /// Communication without any encryption (even password is send as a plain text).
     case none

Sources/Smtp/SmtpServerConfiguration.swift

@@ -7,7 +7,7 @@
 import NIO
 import Vapor
 
-public struct SmtpServerConfiguration {
+public struct SmtpServerConfiguration: Sendable {
     public var hostname: String
     public var port: Int
     public var secure: SmtpSecureChannel