feat: Begin working on configuration client.

Sources/ConfigurationClient/Configuration.swift

@@ -0,0 +1,75 @@
+import Foundation
+
+public struct Configuration: Codable, Sendable {
+  public let target: Target?
+  public let strategy: VersionStrategy?
+
+  public init(
+    target: Target? = nil,
+    strategy: VersionStrategy? = .semvar()
+  ) {
+    self.target = target
+    self.strategy = strategy
+  }
+}
+
+public extension Configuration {
+
+  enum VersionStrategy: Codable, Equatable, Sendable {
+    case branch(Branch = .init())
+    case semvar(SemVar = .init())
+
+    public struct Branch: Codable, Equatable, Sendable {
+      let includeCommitSha: Bool
+
+      public init(includeCommitSha: Bool = true) {
+        self.includeCommitSha = includeCommitSha
+      }
+    }
+
+    public enum PreReleaseStrategy: Codable, Equatable, Sendable {
+      /// Use output of tag, with branch and commit sha.
+      case branch(Branch = .init())
+
+      /// Provide a custom pre-release tag.
+      indirect case custom(String, PreReleaseStrategy? = nil)
+
+      /// Use the output of `git describe --tags`
+      case gitTag
+    }
+
+    public struct SemVar: Codable, Equatable, Sendable {
+      let preReleaseStrategy: PreReleaseStrategy?
+      let requireExistingFile: Bool
+      let requireExistingSemVar: Bool
+
+      public init(
+        preReleaseStrategy: PreReleaseStrategy? = nil,
+        requireExistingFile: Bool = true,
+        requireExistingSemVar: Bool = true
+      ) {
+        self.preReleaseStrategy = preReleaseStrategy
+        self.requireExistingFile = requireExistingFile
+        self.requireExistingSemVar = requireExistingSemVar
+      }
+    }
+  }
+
+  enum Target: Codable, Equatable, Sendable {
+    case path(String)
+    case module(Module)
+
+    public struct Module: Codable, Equatable, Sendable {
+      public let name: String
+      public let fileName: String
+
+      public init(
+        _ name: String,
+        fileName: String = "Version.swift"
+      ) {
+        self.name = name
+        self.fileName = fileName
+      }
+    }
+  }
+}