feat(source): Add Root source test

[chait-slim]

Should be merged after: #4397

[jess-lowe]

/gcbrun

[jess-lowe]

LGTM!

[jess-lowe]

Hey @chait-slim, we attempted to start ingesting into the test instance yesterday, but are getting 405 errors. Would it be possible to add 'HEAD' to the allowed actions list? We do HEAD requests before GET requests to check whether anything actually needs updating to reduce traffic on your end :) Thanks!

[chait-slim]

Hi @jess-lowe I have added a HEAD action:

HTTP/2 200
date: Tue, 06 Jan 2026 14:21:42 GMT
content-type: application/octet-stream
content-length: 792644
etag: "b8693ab49d2d3cc75f53a7c97dd2df81"
last-modified: Tue, 06 Jan 2026 12:00:09 GMT
vary: Origin
cf-cache-status: DYNAMIC
report-to: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https://a.nel.cloudflare.com/report/v4?s=z0Y671M4LwGUJcc%2FB0W8j7IKmMHeGZADD43Sd9%2FnM%2B2XkuWzQaKEWNlBT3FTT%2BFHtJdt8ho1DNX5yCVJYJx5PCTEu2AtanlUROY%3D"}]}
nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800}
server: cloudflare
cf-ray: 9b9bdd01c818b2ed-TLV
alt-svc: h3=":443"; ma=86400