Add migration for changed containerd config template path

[tjkirch]

We changed the path to the containerd config template file in #613 to support
image variants, and we need a migration to update existing installations.

Testing done:

0.2.0 path:

$ cat datastore-sample/current/live/configuration-files/containerd-config-toml/template-path; echo
"/usr/share/templates/containerd-config-toml"

Migrate up:

$ cargo run -- --log-level trace --datastore-path datastore-sample/current --migration-directories ./migration-binaries --migrate-to-version 0.2
...
19:58:04 [DEBUG] (1) migrator: Sorted migrations: ["migrate_v0.2_containerd-config-path"]
19:58:04 [ INFO] Copying datastore from /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.1_kZNHRvDkARjcHinw to work location /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.2_Dce4ixf0zQNvT6gb
19:58:04 [ INFO] Running migration command: "./migration-binaries/migrate_v0.2_containerd-config-path" "--forward" "--datastore-path" "/home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.2_Dce4ixf0zQNvT6gb"
19:58:04 [DEBUG] (1) migrator: Migration stdout: 
19:58:04 [DEBUG] (1) migrator: Migration stderr: 
19:58:04 [ INFO] Flipping /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.2 to point to v0.2_Dce4ixf0zQNvT6gb
19:58:04 [ INFO] Flipping /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0 to point to v0.2

0.2.1 path:

$ cat datastore-sample/current/live/configuration-files/containerd-config-toml/template-path; echo
"/usr/share/templates/containerd-config-toml_aws-k8s"

Migrate down:

$ cargo run -- --log-level trace --datastore-path datastore-sample/current --migration-directories ./migration-binaries --migrate-to-version 0.1
...
19:58:21 [DEBUG] (1) migrator: Sorted migrations: ["migrate_v0.2_containerd-config-path"]
19:58:21 [ INFO] Copying datastore from /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.2_Dce4ixf0zQNvT6gb to work location /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.1_aEOHCFfM25xykQ7J
19:58:21 [ INFO] Running migration command: "./migration-binaries/migrate_v0.2_containerd-config-path" "--backward" "--datastore-path" "/home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.1_aEOHCFfM25xykQ7J"
19:58:21 [DEBUG] (1) migrator: Migration stdout: 
19:58:21 [DEBUG] (1) migrator: Migration stderr: 
19:58:21 [ INFO] Flipping /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0.1 to point to v0.1_aEOHCFfM25xykQ7J
19:58:21 [ INFO] Flipping /home/ANT.AMAZON.COM/tjk/work/thar/workspaces/api/migration/migrator/datastore-sample/v0 to point to v0.1

Back to 0.2.0 path:

$ cat datastore-sample/current/live/configuration-files/containerd-config-toml/template-path; echo
"/usr/share/templates/containerd-config-toml"

[zmrow]

🏒

[zmrow]

While not directly related to this PR (and perhaps deserving of its own issue), do we want this migrations section to contain only the migrations for the current release? Or all migrations?

[tjkirch]

We had talked about it in a team meeting previously and decided it should only be for the current release, but I fully expect this file format to change quite a bit.