fix(api): Set API identifying headers on all HTTP requests (CODY-4209)

[jamesmcnamara]

Closes CODY-4209

Sets the X-Requested-With flag on all HTTP requests. I tested this locally with VSCode, Eclipse, JetBrains, Cody Web and the Cody CLI and for each of them (in concert with these two other PRs) saw the headers appear in the logs when I made a chat interaction.

• VSCode identifies as vscode
• JetBrains identifies as jetbrains
• Eclipse identifies as eclipse
• Cody Web identifies as web
• Cody CLI identifies as cody-cli

We might consider either prepending each name with sourcegraph- if we want to be very explicit that it's our apps, but I think it's pretty clear with the current values and it's consistent with the clientName and CodyIDE values used through out the codebase today.

The one tricky bit here is Cody Web because at least when developing locally, the requests to the SG instance are CORS requests and by default the local server is not a trusted origin. In the two linked PRs I added the headers to the trusted list and added the default vite server URL to the local trusted origins. I think that we shouldn't have to do anything for production because they shouldn't be CORS requests then right?

Are there any other places might I need to check or update to make sure this works?

Edit: I just added the if statement to exclude these headers if we're in development mode. If we like that I can probably close the dev-private PR and we won't have to make any changes to S2.

Test plan

Tested manually to see that the HTTP header was present

Changelog

Sets the X-Requested-With header on all HTTP requests.

[dadlerj]

Approved from a property naming perspective. I defer to @vovakulikov to review the code changes :)