Feat: Add custom user agent for Monika

[dennypradipta]

Monika Pull Request (PR)

What feature/issue does this PR add

This PR adds custom user agent when probing websites, and will fixes #1292

How did you implement / how did you fix it

1. Add logic for handling user agents from config
2. Add default value for user agent
3. Add flag for user agent

How to test

1. Create a simple fastify server:

   
   // Import the framework and instantiate it
   import Fastify from "fastify";

const fastify = Fastify({ logger: { serializers: { req(req) { console.log(req.headers["user-agent"]);

    return {
      userAgent: req.headers["user-agent"],
    };
  },
},

}, });

// Declare a route fastify.get("/", async function handler(request, reply) { return { hello: "world" }; });

// Run the server! try { await fastify.listen({ port: 3000 }); } catch (err) { fastify.log.error(err); process.exit(1); }

2. Run the server
3. Run Monika pointing to the local server
4. Pay attention to the user agent

## Video
https://github.com/hyperjumptech/monika/assets/16670475/67920681-af24-47e2-8117-a6c67c7cf972

[dennypradipta]

Still verifying whether if the Docker version uses the custom user agent.

[haricnugraha]

I just remembered Monika has getContext().userAgent. The value is @hyperjumptech/monika/1.20.2 (darwin-x64) node-20.11.0.

[dennypradipta]

I just remembered Monika has getContext().userAgent. The value is @hyperjumptech/monika/1.20.2 (darwin-x64) node-20.11.0.

Thanks for the tip! It works flawlessly

Docker

NPM

[dennypradipta]

Here is the example for using custom user agent