Create content validation feature flag

Use feature flag to enable/disable content validation feature

assigned to @daveliu

By dave liu on 2021-10-28T00:58:40 (imported from GitLab)

changed the description

By dave liu on 2021-10-28T00:56:10 (imported from GitLab)

changed time estimate to 24h

By dave liu on 2021-10-28T00:56:24 (imported from GitLab)

assigned to @daveliu

By dave liu on 2021-10-28T00:57:29 (imported from GitLab)

After discussion, we think as we already have enable/disable checkbox in admin panel, we don't need another feature flag for it, so close this issue

By dave liu on 2021-11-15T07:34:24 (imported from GitLab)