docs: add migration guide for ownCloud to oCIS

[DeepDiver1975]

Summary

• Adds migrating_to_ocis.adoc — a full migration guide covering prerequisites (OC10 and oCIS), all seven migration steps with commands, and a dedicated section for LDAP-based migrations
• Adds _migrate_to_ocis_commands.adoc — occ command reference documenting all seven migrate:to-ocis:* commands with arguments and options
• Updates navigation and occ_command.adoc to include the new page and command reference

Test plan

• Build the docs locally with npm run antora-dev-local and verify the new page renders correctly
• Check all internal xrefs resolve (migrating_to_ocis ↔ occ_command section)
• Verify the nav entry appears in the correct location under Maintenance
• Review content accuracy against the owncloud/migrate_to_ocis README and PHP source

🤖 Generated with Claude Code

[jvillafanez]

Looks good to me

[dj4oC]

LGTM
Will test later but this should not block the PR

[mmattel]

I did a local rendering and found things to improve/fix, BUT (first findings)

1. What is not migrated. There is no mentioning about data from external drives, pls clarify.
   • Drives the user has added
   • Drives created by the admin and has shared
   • Shares to external drives
2. When migrating local oc10 Users/Role/Groups to ocis/IDM (no LDAP), has this has been fully tested? We explicitly note that the ocis internal IDM has a very limited scope. Can one please proof this kind of migration has been tested and works.
3. In section Migration with LDAP Users:
   For me, this reads the following, pls verify:
   • Users and groups are not migrated but need to exist on the LDAP ocis is connected to.
   • Some prerequisites need to be met on the OC10 side such as the email and username attribute.
   • Additional ocis envvars need to be set.
4. When migrating user file data (rsync), is the data being migrated into the users personal Space? There is no mentioning about this

Adding more comments when finding things.

[DeepDiver1975]

@jvillafanez can you please clarify? Thank you

[jvillafanez]

What is not migrated. There is no mentioning about data from external drives, pls clarify.
Drives the user has added
Drives created by the admin and has shared
Shares to external drives

When migrating the files, the rclone command uses '--webdav-owncloud-exclude-shares=true' '--webdav-owncloud-exclude-mounts=true', so I assume neither drives nor shares will be migrated. The share migration will happen from the source owner, not from the receiving side, and based on the existing files in oCIS (files that should have been migrated).
To clarify, if A shares with B, then B won't receive a copy of the files shared by A, but he will be able to access to the file via a new share that A will create during the share migration. Basically, the state in oCIS should be the same as in OC10.

When migrating local oc10 Users/Role/Groups to ocis/IDM (no LDAP), has this has been fully tested? We explicitly note that the ocis internal IDM has a very limited scope. Can one please proof this kind of migration has been tested and works.

Users, groups and group membership will be kept, but not roles. You need to use a default role for all the migrated users (likely "user"), and the same role will be used for all of them regardless of the OC10 role they have.

If they have multiple admins in OC10 in the "admin" group, all those users will also be in the oCIS "admin" group but without admin privileges (unless they choose to make everyone admin). The actual oCIS admin should manually set the appropriate role only for those users.
As for OC10 subadmins, I don't think we have a matching role in oCIS, so it will be ignored.

When migrating user file data (rsync), is the data being migrated into the users personal Space? There is no mentioning about this

Yes. All the user files will be migrated to their respective oCIS account, assuming the user has been correctly migrated.

[DeepDiver1975]

@mmattel feedback has been incorporated

[mmattel]

thx, I am working on additional required updates and fixes

[mmattel]

@dj4oC @jvillafanez I have updated and fixed the document and created a rendered build on staging.

[dj4oC]

@dj4oC @jvillafanez I have updated and fixed the document and created a rendered build on staging.

Thank you. Looks good to me.

[mmattel]

Just a note before merging: there are three real life scenarios migrating users (oc10 to ocis):

1. local to IDM
2. local to LDAP
3. LDAP to LDAP

ONLY (1) has bee tested because it is based on the migration app. But it is the most irrelevant one for enterprises and for the community only relevant if one wants to play around.

For the other ones (2,3) no testing/QA has been made so far or feedback for the QA provided.