Schema differences compared to CE

After the CE/EE backport (https://gitlab.com/gitlab-org/gitlab-ee/issues/11252), we are still seeing differences in db/schema.rb when comparing CE and EE.

Additionally, when I merged the CE MR https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29747 before merging the corresponding EE MR https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/12653, the changes to db/schema.rb from the CE MR were not merged automatically into the EE project presumably because of a conflict.

As @tkuah pointed out on Slack, we seem to use --ours merge strategy for the schema file: https://gitlab.com/gitlab-org/merge-train/blob/f1a07690607bd03cdd3aaeb369fa8d2ccbfdfe79/bin/merge-db-schema#L183

We should clarify

• if db/schema.rb should be identical across CE/EE from now on
• if the merge strategy is still needed