Add option to configure the cursor/param name

[marianposaceanu]

Description

This pull request adds the ability to customize the cursor query parameter name.

Changes

The cursor_name configuration option can now be set to a custom value in the GearedPagination.configure block. By default, the cursor parameter is named :page, but it can now be customized.

The reason for this change is to provide more flexibility for developers who may want to use a different query parameter name for pagination cursors, for example to avoid conflicts with other query parameters in their application or where the FE expects a specific name for the cursor param.

Usage

GearedPagination.configure do |config|
  config.cursor_name = :cursor
end

You can also use the cursor parameter name in your links to generate pagination URLs:

<%= link_to "Next page", messages_path(cursor: @page.next_param) %>

This will generate a URL with a ?cursor=<next_cursor> query parameter instead of ?page=<next_page>.

Additional Notes

This pull request includes tests to ensure that the cursor_name option is working as expected, and that links with custom cursor parameter names are generated correctly.