good first issue
Description
There is a limit set on the maximum API request body size. That limit is currently hardcoded to 1mb (https://github.com/gristlabs/grist-help/pull/320#issuecomment-2021537352). It would be good to make this configurable, in the same way that related parameters like GRIST_MAX_UPLOAD_IMPORT_MB and GRIST_MAX_UPLOAD_ATTACHMENT_MB are.