fix: resolved wrong pagination info

[andrea-deri]

This PR contains a fix made on pagination during the retrieve of the mock resources list. The fix provide the execution of a dedicated query for retrieve the total number of elements in the whole collection, resolving a bug that caused a wrong value for the count of elements in page.

List of Changes

• Refactored query for get the count of all elements
• Added new field for retrieve the total number of elements
• Added @Indexed annotation on mock resource entity

Motivation and Context

This fix permits to resolve a little bug on pagination

How Has This Been Tested?

• Tested in local environment

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

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