migration error in stderr when downgrading from v1.16.1 to v1.15.1

[webern]

I saw these errors when I downgraded from develop:b375585ce32e61a2d796a1f9eff9d374964fa813 (version in Release.toml is v1.16.1) to an image built at the v1.15.1 tag.

Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.1_updog-network-affected.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_schnauzer-v2-generators.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_public-control-container-v0-7-5.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_aws-control-container-v0-7-5.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [ERROR] Migration stderr: 'settings.host-containers.control.source' has no 'template' key in metadata
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_public-admin-container-v0-11-1.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_aws-admin-container-v0-11-1.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [ERROR] Migration stderr: 'settings.host-containers.admin.source' has no 'template' key in metadata
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_kernel-modules-autoload-settings.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_kernel-modules-autoload-restart.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_kernel-modules-autoload-files.lz4'
Nov 29 19:33:13 localhost migrator[941]: 19:33:13 [INFO] Running migration 'migrate_v1.16.0_kernel-modules-autoload-configs.lz4'

[cbgbt]

This is a bug in this migration.

Prior to schnauzer-v2, template-based settings generators had two critical pieces of datastore-based metadata:

• The template, which told the generator what template string to render
• The setting-generator, which told the generator how to invoke schnauzer to render the template.

Moving to schnauzer-v2, the template became irrelevant. The migration "up" preserved that metadata in case of a downwards migration; however, if you downgrade from 1.16.0 to 1.15.1 without a previous upgrade first, you will not have this metadata. The migration needs to be modified to explicitly insert this metadata.

I'll submit a fix.