various improvements

[EvanBldy]

Problem

• The error stack trace is shown when in production.
• In "/config", there are no default_locale and default_timezone.
• Tokens for slack, mattermost, and discord are shown in some routes for non-admin persons.
• In "/user/context", as an admin, we don't know the user limit.
• Some requirements are outdated.
• For csv exports/imports with metadata checklist values are not always properly formatted.
• Sometimes we use the "page_size" parameter for pagination limit instead of "limit".
• For "data/project/<project_id>/comments" there's no "limit" parameter.
• On Zou remote/nomad, we don't get files by chunks, we download them and write them fully in memory.

Solution

• Only show error stack trace in debug.
• In "/config", add default_locale and default_timezone.
• Tokens for slack, mattermost, and discord are now only shown for admin persons.
• In "/user/context", as an admin, add user_limit.
• Upgrade outdated requirements.
• For csv exports/imports with metadata checklist values are now properly formatted.
• Change "page_size" parameter for pagination with "limit".
• For "data/project/<project_id>/comments", add "limit" parameter.
• On Zou remote/nomad, get files by chunks.