Implement export/import of view definitions as JSON/YAML

[niteshpurohit]

Feature Request

Description:

Add functionality to export all materialized view definitions to a JSON or YAML file, and to import them from such a file.

Use Case:

This is useful for backing up definitions, migrating them between environments (e.g., staging to production), and keeping them in version control.

Proposed Solution:

• Create two new rake tasks: mat_views:export[format] and mat_views:import[file_path].
• The export task will serialize all MatViewDefinition records.
• The import task will read the file, and then create or update definitions in the database.

RSpec Tests:

• Create several view definitions.
• Run mat_views:export and verify the output file is created and has the correct content.
• Delete the definitions from the database.
• Run mat_views:import with the exported file.
• Verify that all definitions are restored correctly in the database.

Checklist:

• I have searched for a similar feature request and didn't find any duplicates.
• I have included all the required information.
• I have tagged the issue with the label "enhancement".

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