Add 'migrate' task to support migration to the specmesh way

[bluemonk3y]

Automation tasks should be used to help existing installations migrate to SpecMesh.

This could look like:

1. User write simple-app with proposed domain id 'somedomain-id'

• channel names are completed using the proposed naming. i.e. _public.somedata
• channels are annotated with migrate-source tags.

i.e.

<snip>
  _protected.retail.subway.food.purchase:
    bindings:
      kafka:
    publish:
      tags: [
        name: "migrate-source: existing-topic.blah-stuff.withmessy-name"
      ]
<snip>

2. User applies extract command to the spec and an existing cluster (should be production)
   simple-template.app is enriched with the topic config, and schema. Schema file is downloaded to the /schema folder.

<snip>
  _protected.retail.subway.food.purchase:
    bindings:
      kafka:
        partitions: 10
        configs:
          cleanup.policy: delete
          retention.ms: 9900000
    publish:
      tags: [
        name: "migrate-source: existing-topic.blah-stuff.withmessy-name"
      ]
        payload:
          $ref: "/schema/simple.schema_demo._public.user_info.proto"
<snip>

3. User applies migrate task. This task will

• create a topic (if it doesn't exist) and configure it with associated settings
• copy topic offsets from the old to new topic
• copy topic data from the old topic to the new topic

4. Client apps should be pointed to the new topic. They should also use the new domain-id/credentaisls so that ACLs are enforced