Support storing user config without dedicated user table

[BenediktSeidlSWM]

This patch introduces a setting 'store_config_by_userid' which is true by default. When set to false, the user config is stored in a table user_infos with the username as its primary key. This allows storing user settings without requiring the usage of the qwc user management api, eg. by using the qwc-oidc-auth service. The schema of the user_infos table omits the user_id column and otherwise depends on the user_info_fields config just as the default setup.

This patch is built similarly to the implementation in qwc-permalink-service, especially this function.

[manisandro]

This relies on a custom user_infos table, with a username column and without the user_id column though, right?

For the oidc-auth there was a recent change to sync the users to the config db [1].

[1] qwc-services/qwc-oidc-auth@de8f9e3

[BenediktSeidlSWM]

Yes, this patch needs a user_infos table without the user_id column. I just saw the new commits in qwc-oidc-auth to sync the users table. Is this the general direction you want to go forward to? In general it would be nice since it would remove the need for special case handling as in qwc-permalink-service altogether. In that case, I would close this PR and try to setup the syncing of users.

[manisandro]

Yes I'd opt for syncing the users rather than introducing special handling in the various services.