Announcements Refactoring

[renatodellosso]

Intro

We're refactoring announcements to allow multiple content types in emails.

Acceptance Criteria

• Replace Announcements's body field with a JsonB column titled content. Add a subject text column.
• Add a template column to Announcements. It should be a boolean that default to false.
• Edit AnnouncementService to validate the schema of content (using that instead of body); use Zod to ensure it matches Juno's schema. See the schema here.

Resources

• Drizzle docs on JsonB