Documentation with latest guidance, and adjust types accordingly

.gitignore

@@ -6,3 +6,5 @@
 xcuserdata/
 .swiftpm
 /Package.resolved
+.history
+.vscode

Docs/README.md

@@ -0,0 +1,3 @@
+# Documentation landing page
+
+This documentation target exists only to serve as a landing page for self hosted documentation.

Docs/SwiftDistributedTracing/Docs.docc/index.md

@@ -0,0 +1,29 @@
+# ``SwiftDistributedTracing``
+
+A Distributed Tracing API for Swift.
+
+## Overview
+
+This is a collection of Swift libraries enabling the instrumentation of server side applications using tools such as tracers. Our goal is to provide a common foundation that allows to freely choose how to instrument systems with minimal changes to your actual code.
+
+While Swift Distributed Tracing allows building all kinds of _instruments_, which can co-exist in applications transparently, its primary use is instrumenting multi-threaded and distributed systems with Distributed Traces.
+
+### Quickstart Guides
+
+We provide a number of guides aimed at getting your started with tracing your systems and have prepared them from three "angles":
+
+1. **Application developers** who create server-side applications
+    * please refer to the <doc:TraceYourApplication> guide.
+2. **Library/Framework developers** who provide building blocks to create these applications
+    * please refer to the <doc:InstrumentYourLibrary> guide. 
+3. **Instrument developers** who provide tools to collect distributed metadata about your application
+    * please refer to the <doc:ImplementATracer> guide.
+
+
+## Topics
+
+### Guides
+
+- <doc:TraceYourApplication>
+- <doc:InstrumentYourLibrary>
+- <doc:ImplementATracer>

Docs/SwiftDistributedTracing/empty.swift

@@ -0,0 +1,19 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Distributed Tracing open source project
+//
+// Copyright (c) 2020-2021 Apple Inc. and the Swift Distributed Tracing project
+// authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! //
+// This module is left purposefully empty of any source files, as it serves
+// only as a "landing page" for the documentation. This is in-place until docc
+// gains the ability to support package-wide documentation.
+// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! //

Package.swift

@@ -8,7 +8,9 @@ let package = Package(
         .library(name: "Tracing", targets: ["Tracing"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/apple/swift-distributed-tracing-baggage.git", .upToNextMinor(from: "0.4.1")),
+        .package(url: "https://github.com/apple/swift-distributed-tracing-baggage", .upToNextMinor(from: "0.4.1")),
+        // .package(url: "https://github.com/apple/swift-log.git", from: "1.4.4"),
+        .package(url: "https://github.com/ktoso/swift-log", .branch("wip-baggage-in-handlers-but-not-api")),
         .package(url: "https://github.com/apple/swift-docc-plugin", from: "1.0.0"),
     ],
     targets: [
@@ -19,6 +21,7 @@ let package = Package(
             name: "Instrumentation",
             dependencies: [
                 .product(name: "InstrumentationBaggage", package: "swift-distributed-tracing-baggage"),
+                .product(name: "Logging", package: "swift-log"),
             ]
         ),
         .testTarget(

Package@swift-5.2.swift

@@ -9,6 +9,7 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-distributed-tracing-baggage.git", .upToNextMinor(from: "0.4.1")),
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.4.4"),
     ],
     targets: [
         // ==== --------------------------------------------------------------------------------------------------------
@@ -18,6 +19,7 @@ let package = Package(
             name: "Instrumentation",
             dependencies: [
                 .product(name: "InstrumentationBaggage", package: "swift-distributed-tracing-baggage"),
+                .product(name: "Logging", package: "swift-log"),
             ]
         ),
         .testTarget(

Package@swift-5.3.swift

@@ -9,6 +9,7 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-distributed-tracing-baggage.git", .upToNextMinor(from: "0.4.1")),
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.4.4"),
     ],
     targets: [
         // ==== --------------------------------------------------------------------------------------------------------
@@ -18,6 +19,7 @@ let package = Package(
             name: "Instrumentation",
             dependencies: [
                 .product(name: "InstrumentationBaggage", package: "swift-distributed-tracing-baggage"),
+                .product(name: "Logging", package: "swift-log"),
             ]
         ),
         .testTarget(

Package@swift-5.4.swift

@@ -9,6 +9,7 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-distributed-tracing-baggage.git", .upToNextMinor(from: "0.4.1")),
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.4.4"),
     ],
     targets: [
         // ==== --------------------------------------------------------------------------------------------------------
@@ -18,6 +19,7 @@ let package = Package(
             name: "Instrumentation",
             dependencies: [
                 .product(name: "InstrumentationBaggage", package: "swift-distributed-tracing-baggage"),
+                .product(name: "Logging", package: "swift-log"),
             ]
         ),
         .testTarget(

Package@swift-5.5.swift

@@ -9,6 +9,7 @@ let package = Package(
     ],
     dependencies: [
         .package(url: "https://github.com/apple/swift-distributed-tracing-baggage.git", .upToNextMinor(from: "0.4.1")),
+        .package(url: "https://github.com/apple/swift-log.git", from: "1.4.4"),
     ],
     targets: [
         // ==== --------------------------------------------------------------------------------------------------------
@@ -18,6 +19,7 @@ let package = Package(
             name: "Instrumentation",
             dependencies: [
                 .product(name: "InstrumentationBaggage", package: "swift-distributed-tracing-baggage"),
+                .product(name: "Logging", package: "swift-log"),
             ]
         ),
         .testTarget(