infra: deprecate edge assignments bespoke URL; route via fscdn.eppo.c…

[leoromanovsky]

…loud

---

labels: mergeable

Fixes: #issue

Motivation and Context

Tidying things up with a change to our routing at the VCL layer; just deployed to production without incident.

Goals

• All traffic to edge assignment will go through the existing CDN route - this gives us a consistent SSL cert, request logging, paves the way to easily support off-boarding and provides a clear delineation between edge and origin requests.

Done

• Deprecating the https://fs-edge-assignment.eppo.cloud/ domain in favor of serving all traffic through our existing https://fscdn.eppo.cloud/
• All requests to /api are routed to the Eppo origin servers and use the Fastly cache and shielding - no change here except to explicitly make it a catch all for that pattern.
• All requests to /edge go to the edge handler
• Created new routes on the server for /edge/assignments that are handled by the same function
  https://github.com/Eppo-exp/eppo/commit/52b7c76c107e723d324b2f0a72702a22f3d32d21

Next steps:

• Updating JS commons, Dart and eppo_core to use the new routing; will be released as a patch to increase customer adoption.
• After traffic stops on the old domain it will be removed

Description

Changes just the precompute client base url to https://fscdn.eppo.cloud/edge - we do not yet have customers that are using a proxy here and I believe this is a safe change to release as a patch.

How has this been tested?

 curl -v -X POST "https://fscdn.eppo.cloud/edge/assignments?apiKey=XYZ" \
     -H "Content-Type: application/json" \
     -d '{
           "subject_key": "your_subject_key_value",
           "subject_attributes": {
            "numeric": {},
            "categorical": {}
           }
         }'
Note: Unnecessary use of -X or --request, POST is already inferred.
* Host fscdn.eppo.cloud:443 was resolved.
* IPv6: (none)
* IPv4: 151.101.201.91
*   Trying 151.101.201.91:443...
* Connected to fscdn.eppo.cloud (151.101.201.91) port 443
* ALPN: curl offers h2,http/1.1
* (304) (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/cert.pem
*  CApath: none
* (304) (IN), TLS handshake, Server hello (2):
* (304) (IN), TLS handshake, Unknown (8):
* (304) (IN), TLS handshake, Certificate (11):
* (304) (IN), TLS handshake, CERT verify (15):
* (304) (IN), TLS handshake, Finished (20):
* (304) (OUT), TLS handshake, Finished (20):
* SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256 / [blank] / UNDEF
* ALPN: server accepted h2
* Server certificate:
*  subject: CN=fscdn.eppo.cloud
*  start date: Feb 12 14:52:46 2025 GMT
*  expire date: May 13 14:52:45 2025 GMT
*  subjectAltName: host "fscdn.eppo.cloud" matched cert's "fscdn.eppo.cloud"
*  issuer: C=US; O=Let's Encrypt; CN=R10
*  SSL certificate verify ok.
* using HTTP/2
* [HTTP/2] [1] OPENED stream for https://fscdn.eppo.cloud/edge/assignments?apiKey=XYZ
* [HTTP/2] [1] [:method: POST]
* [HTTP/2] [1] [:scheme: https]
* [HTTP/2] [1] [:authority: fscdn.eppo.cloud]
* [HTTP/2] [1] [:path: /edge/assignments?apiKey=XYZ
* [HTTP/2] [1] [user-agent: curl/8.7.1]
* [HTTP/2] [1] [accept: */*]
* [HTTP/2] [1] [content-type: application/json]
* [HTTP/2] [1] [content-length: 169]
> POST /edge/assignments?apiKey=XYZ
> Host: fscdn.eppo.cloud
> User-Agent: curl/8.7.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 169
>
* upload completely sent off: 169 bytes
< HTTP/2 200
< content-type: application/json
< access-control-allow-origin: *
< access-control-allow-methods: GET, POST, OPTIONS
< accept-ranges: bytes
< date: Thu, 13 Mar 2025 20:44:38 GMT
< via: 1.1 varnish
< x-served-by: cache-pao-kpao1770043-PAO, cache-pao-kpao1770045-PAO
< x-cache: MISS
< x-cache-hits: 0
< x-timer: S1741898679.621554,VS0,VE281
< content-length: 26392
<
{"obfuscated":true,"format":"PRECOMPUTED","salt":"A16eSdI0vokS02deVdSv4Q","createdAt":"2025-03-13T20:44:38.897694825Z","environment":{"name":"eppo.cloud"},"flags":