api(images): allow HEAD request on image/full

[keturn]

Some clients, including whatever GIMP uses when you do "Open Location", do a HEAD request on a resource before downloading it.

Currently the image route only supports GET, so the HEAD request fails.

This lack of support for HEAD requests is something that should be addressed generally:

• Automatically support HEAD method for all GET routes, as Starlette does fastapi/fastapi#1773

but in the meantime, I guess we handle it on a case-by-case basis? This PR adds HEAD to the route for {image}/full.

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update
• Community Node Submission

QA Instructions, Screenshots, Recordings

Test instructions:

• get the URL for a full image, perhaps by doing right-click Open in New Tab and copying that URL.
• issue a HTTP HEAD request for that URL (maybe using httpie or your other favorite HTTP test client) or with File/Open Location in GIMP.
• ensure the request receives a 200 OK response and/or the image opens.

[psychedelicious]

LGTM

❯ curl --head http://localhost:5173/api/v1/images/i/755d703e-f47d-436f-be3f-2920fc203d4c.png/full
HTTP/1.1 200 OK
Access-Control-Allow-Origin: *
date: Tue, 08 Aug 2023 03:04:52 GMT
server: uvicorn
content-type: image/png
content-disposition: inline; filename="755d703e-f47d-436f-be3f-2920fc203d4c.png"
cache-control: max-age=31536000
content-length: 424646
last-modified: Mon, 07 Aug 2023 14:00:09 GMT
etag: 0138f253d3b3a77902408f2514e29362
connection: close