FINERACT-1926: Add previous owner to ExternalAssetOwnerTransfer

[oleksii-novikov-onix]

Description

Describe the changes made and why they were made.

Ignore if these details are present on the associated Apache Fineract JIRA ticket.

Checklist

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• Write the commit message as per https://github.com/apache/fineract/#pull-requests
• Acknowledge that we will not review PRs that are not passing the build ("green") - it is your responsibility to get a proposed PR to pass the build, not primarily the project's maintainers.
• Create/update unit or integration tests for verifying the changes made.
• Follow coding conventions at https://cwiki.apache.org/confluence/display/FINERACT/Coding+Conventions.
• Add required Swagger annotation and update API documentation at fineract-provider/src/main/resources/static/legacy-docs/apiLive.htm with details of any API changes
• Submission is not a "code dump". (Large changes can be made "in repository" via a branch. Ask on the developer mailing list for guidance, if required.)

FYI our guidelines for code reviews are at https://cwiki.apache.org/confluence/display/FINERACT/Code+Review+Guide.

[adamsaghy]

LGTM