[Feature request] Scaffold MCP server project with func init

[lilyjma]

Description

For hosting BYO MCP servers (servers built with the official MCP SDKs), we need to run them as custom handlers. As a result, certain boilerplate artifacts need to be added to a project. This is a request to have the func init command, when specified with mcp server as the type, to add the boilerplate files so the process can be streamlined for customers.

Requirements

1. Introduce MCP type app to func init

   func init --configurationProfile mcp-custom-handler --transport streamable-http 

   The command would follow with prompts to help fill out specific values in host.json so customers don't need to go back to fill them:

   • "What is the language of your server?"
     • Options: Node, Python, .NET
   • "What is the command to run your MCP server? Examples include npm, python, dotnet."
     • If an unsupported option (like "uv") is entered by the customer, present the supported options, which are "node", "npm", "python", "dotnet"
   • Depending on prompt 1's answer
     • If it's Python, "What's the path to the main script? For example, weather.py"
     • If it's Node, "What are the arguments for running the MCP server? For example, run start"
     • If it's .NET, "What's the path to the compiled DLL? For example, weather.dll"

   Based on the answers, the host.json for a Node server could look like

       {
           "version": "2.0",
           "configurationProfie": "mcp-custom-handler",
           "customHandler": {
               "description": {
                   "defaultExecutablePath": "npm",
                   "workingDirectory": "",
                   "arguments": ["run start"]
               }
            }
       }

   For Python -

   { 
           "version": "2.0",
           "configurationProfie": "mcp-custom-handler",
           "customHandler": {
               "description": {
                   "defaultExecutablePath": "python",
                   "workingDirectory": "",
                   "arguments": ["weather.py"]
               }
            }
       }

   For .NET -

   { 
           "version": "2.0",
           "configurationProfie": "mcp-custom-handler",
           "customHandler": {
               "description": {
                   "defaultExecutablePath": "dotnet",
                   "workingDirectory": "",
                   "arguments": ["QuickstartWeatherServer.dll"]
               }
            }
       }
   

2. A local.settings.json is added as well

   {
       "IsEncrypted": false,
       "Values": {
           "FUNCTIONS_WORKER_RUNTIME": "<python, node, or dotnet-isolated>"
       }
   }

3. If the language is Python, prompt the customer to add a requirements.txt if they don't already have it: "A requirements.txt is required today as pyproject.toml is not yet supported."

4. If the language is .NET, add a .azurefunctions directory with an empty file called "required.txt". This is required for successful deployment.

Note: This is a proposal for a new experience that's not available yet. Please don't copy/paste in your app as it won't work.