Determine method for adding new build task types

[drewbo]

Once the first task type is complete, consider how new tasks will be added. Two potential options are via the admin UI or via database migrations

Acceptance Criteria

• Determine next steps and acceptance criteria

[drewbo]

To ensure consistency between environments, it will be easiest to add new task types via migration. A rough outline of adding a new type:

• add a new CF task in each environment (ideally via concourse)
• add a migration which takes env as an environment variable, uses it to add the required metadata for the new build task

[drewbo]

After the task type exists, we should separately consider how to add a new site_build_task