default config for 100MB uploads

[wardi]

CKAN defaults to allow 10MB uploads but nginx defaults to only allow 1MB body size.

Both of those are too small. Let's default to allow 100MB uploads and increase nginx to allow the same (with some room for base64 encoding overhead).

Having these options in the docker config also makes it easier for users to find where to change them.

[wardi]

I didn't resolve another issue related to this. If nginx is rejecting an upload it serves users a 404 error page because it can't find an error.html file:

nginx-1  | 2024/10/08 19:24:34 [error] 9#9: *2 client intended to send too large body: 40242340 bytes, client: 172.23.0.1, server: localhost, request: "POST /dataset/foo/resource/new HTTP/1.1", host: "localhost:8443", referrer: "https://localhost:8443/dataset/foo/resource/new"
nginx-1  | 2024/10/08 19:24:34 [error] 9#9: *2 open() "/usr/share/nginx/html/error.html" failed (2: No such file or directory), client: 172.23.0.1, server: localhost, request: "POST /dataset/foo/resource/new HTTP/1.1", host: "localhost:8443", referrer: "https://localhost:8443/dataset/foo/resource/new"

We ought to fix that in our image by adding this error.html or maybe by pulling a fix from upstream that includes a default error page?