Prevent terminal relaunch on extension load

.devcontainer/devcontainer.json

@@ -1,7 +1,7 @@
 // For format details, see https://aka.ms/devcontainer.json
 {
 	"name": "pallets/flask",
-	"image": "mcr.microsoft.com/devcontainers/python:3",
+	"image": "mcr.microsoft.com/vscode/devcontainers/python:3",
 
 	// Configure tool-specific properties.
 	"customizations": {
@@ -11,16 +11,16 @@
 			"settings": {
 				// Settings for the python extension.
 				"python.defaultInterpreterPath": "${workspaceFolder}/.venv",
-				"python.terminal.activateEnvInCurrentTerminal": true
+				"python.terminal.activateEnvInCurrentTerminal": true,
+				// Prevent the terminal from refreshing on extension load.
+				"terminal.integrated.environmentChangesRelaunch": false
 			}
-		},
-		"codespaces": {
-			"openFiles": [
-				".devcontainer/codespaces-welcome-message.txt"
-			]
 		}
 	},
 
+	// Displays a custom welcome message.
+	"onCreateCommand": "sudo cp .devcontainer/welcome-message.txt /usr/local/etc/vscode-dev-containers/first-run-notice.txt",
+
 	// Runs the initial setup commands after the container is created.
 	"postCreateCommand": "sudo chmod +x .devcontainer/post-create-command.sh && .devcontainer/post-create-command.sh"
 }