Explicitly mark the AsyncSequence iterators as non Sendable (#490)

Author: fabianfett

Package.swift

@@ -2,7 +2,7 @@
 import PackageDescription
 
 let swiftSettings: [SwiftSetting] = [
-    .enableUpcomingFeature("StrictConcurrency")
+    .enableUpcomingFeature("StrictConcurrency"),
 ]
 
 let package = Package(

Sources/PostgresNIO/New/PostgresNotificationSequence.swift

@@ -20,3 +20,6 @@ public struct PostgresNotificationSequence: AsyncSequence, Sendable {
         }
     }
 }
+
+@available(*, unavailable)
+extension PostgresNotificationSequence.AsyncIterator: Sendable {}

Sources/PostgresNIO/New/PostgresQuery.swift

@@ -26,7 +26,7 @@ extension PostgresQuery: ExpressibleByStringInterpolation {
 }
 
 extension PostgresQuery {
-    public struct StringInterpolation: StringInterpolationProtocol {
+    public struct StringInterpolation: StringInterpolationProtocol, Sendable {
         public typealias StringLiteralType = String
 
         @usableFromInline

Sources/PostgresNIO/New/PostgresRowSequence.swift

@@ -4,7 +4,7 @@ import NIOConcurrencyHelpers
 /// An async sequence of ``PostgresRow``s.
 ///
 /// - Note: This is a struct to allow us to move to a move only type easily once they become available.
-public struct PostgresRowSequence: AsyncSequence {
+public struct PostgresRowSequence: AsyncSequence, Sendable {
     public typealias Element = PostgresRow
 
     typealias BackingSequence = NIOThrowingAsyncSequenceProducer<DataRow, Error, AdaptiveRowBuffer, PSQLRowStream>
@@ -56,6 +56,9 @@ extension PostgresRowSequence {
     }
 }
 
+@available(*, unavailable)
+extension PostgresRowSequence.AsyncIterator: Sendable {}
+
 extension PostgresRowSequence {
     public func collect() async throws -> [PostgresRow] {
         var result = [PostgresRow]()