The `system.group0_history` table provides useful descriptions for each
command committed to Raft group 0. One way of applying a command to
group 0 is by calling `migration_manager::announce`. This function has
the `description` parameter set to empty string by default. Some calls
to `announce` use this default value which causes `null` values in
`system.group0_history`. We want `system.group0_history` to have an
actual description for every command, so we change all default
descriptions to reasonable ones.
Going further, We remove the default value for the `description`
parameter of `migration_manager::announce` to avoid using it in the
future. Thanks to this, all commands in `system.group0_history` will
have a non-null description.
Fixes#13370Closes#14979
* github.com:scylladb/scylladb:
migration_manager: announce: remove the default value of description
test: always pass empty description to migration_manager::announce
migration_manager: announce: provide descriptions for all calls
59c410fb97