Don't use / as webUrl, prefer NEXT_PUBLIC_WEB_URL or VERCEL_URL

[humphd]

Fixes #2102

I thought I could use / as a fallback URL, but i can't. This fix might also not work, but I want to test it on Vercel.

[humphd]

OK, I got this working. I had to update the env variables manually in Vercel to expose the VERCEL_URL to our build script, and expose it as WEB_URL. I also had to add some extra code to prepend https:// to it if it's missing.

While I was doing this, I noticed that we had our vercel.json in the wrong dir, so I moved that too.

[humphd]

I did one more fix to simplify the code in the front-end, and move the https:// prefix logic to the build.

Locally this gives:

Trying to load missing ENV variables from /Users/humphd/repos/telescope/.env
Trying to load missing ENV variables from /Users/humphd/repos/telescope/config/env.development
Using NEXT_PUBLIC_WEB_URL=https://http://localhost:8000
Using NEXT_PUBLIC_API_URL=http://localhost:3000
Using NEXT_PUBLIC_IMAGE_URL=http://localhost/v1/image
Using NEXT_PUBLIC_POSTS_URL=http://localhost/v1/posts
Using NEXT_PUBLIC_AUTH_URL=http://localhost/v1/auth

And on Vercel:

11:05:09.639 | Trying to load missing ENV variables from /.env
11:05:09.639 | Trying to load missing ENV variables from /config/env.development
11:05:09.639 | Using NEXT_PUBLIC_WEB_URL=https://telescope-p5vfj150a-humphd.vercel.app
11:05:09.639 | Using NEXT_PUBLIC_API_URL=https://dev.telescope.cdot.systems
11:05:09.639 | Using NEXT_PUBLIC_IMAGE_URL=https://dev.api.telescope.cdot.systems/v1/image
11:05:09.639 | Using NEXT_PUBLIC_POSTS_URL=https://dev.api.telescope.cdot.systems/v1/posts
11:05:09.640 | Using NEXT_PUBLIC_AUTH_URL=https://dev.api.cdot.systems/v1/auth

Everything looks good.