Add plugin API for custom refresh strategies

[niteshpurohit]

Feature Request

Description:

Create a plugin API that allows developers to define their own custom refresh strategies beyond the default REFRESH MATERIALIZED VIEW command.

Use Case:

This would enable support for other database systems (e.g., Redshift, BigQuery) or custom refresh logic (e.g., incremental updates via INSERT/DELETE) by allowing users to extend the gem's functionality.

Proposed Solution:

• Define a base strategy class with a simple interface (e.g., a refresh method).
• Allow a MatViewDefinition to specify a custom strategy class.
• MatViewRefreshJob would then instantiate and call the specified strategy class instead of its default logic.

RSpec Tests:

• Create a dummy custom refresh strategy class in the test suite.
• Configure a view definition to use this custom strategy.
• Trigger a refresh and verify that the custom strategy's refresh method was called, not the default one.

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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