Automatically open a PR to bump the calver (#4167)

* Update our tools package to Swift 6.1

Also improves the package layout with subdirectories 📁

* Update GenerateSDKMocks to be an Async command.

* Add a tool to bump the project CalVer every month.

* Add a workflow to automatically bump the calendar version.

Note: This only does year & month, the patch is handled by the release script.

Tools/Sources/Commands/GenerateSDKMocks.swift

@@ -0,0 +1,44 @@
+import ArgumentParser
+import CommandLineTools
+import Foundation
+
+struct GenerateSDKMocks: AsyncParsableCommand {
+    enum GenerateSDKMocksError: Error {
+        case invalidFileUrl
+    }
+
+    static let configuration = CommandConfiguration(abstract: "A tool to setup the mocks for the Matrix Rust SDK")
+
+    @Argument(help: "The argument to specify a branch of the SDK. Use `local` to use your local version")
+    var version: String
+
+    private var fileURLFormat = "https://raw.githubusercontent.com/element-hq/matrix-rust-components-swift/%@/Sources/MatrixRustSDK/matrix_sdk_ffi.swift"
+
+    func run() async throws {
+        if version == "local" {
+            try generateSDKMocks(ffiPath: "\(URL.sdkDirectory.path)/bindings/apple/generated/swift")
+        } else {
+            let path = try await downloadSDK(version: version)
+            try generateSDKMocks(ffiPath: path)
+            try FileManager.default.removeItem(atPath: path)
+        }
+    }
+
+    /// Generates the SDK mocks using Sourcery.
+    func generateSDKMocks(ffiPath: String) throws {
+        try Zsh.run(command: "sourcery --sources \(ffiPath) --templates Tools/Sourcery/SDKAutoMockable.stencil --output ElementX/Sources/Mocks/Generated/SDKGeneratedMocks.swift")
+    }
+
+    /// Downloads the specified version of the `matrix_sdk_ffi.swift` file and returns the path to the downloaded file.
+    func downloadSDK(version: String) async throws -> String {
+        let fileURLString = String(format: fileURLFormat, version)
+        guard let fileURL = URL(string: fileURLString) else {
+            throw GenerateSDKMocksError.invalidFileUrl
+        }
+        
+        let (tempURL, _) = try await URLSession.shared.download(from: fileURL)
+        let sdkFilePath = NSTemporaryDirectory().appending("matrix_sdk_ffi.swift")
+        try FileManager.default.moveItem(at: tempURL, to: URL(fileURLWithPath: sdkFilePath))
+        return sdkFilePath
+    }
+}