Use `RalphStatementsQuery` model for query parameters in API `get` signature

[quitterie-lcs]

Purpose

The signature of get statements method in API router is highly descriptive and can be quite long and confusing to read and understand for developers. Most part of this signature is the LRS query parameter for Statements Resource.

Furthermore, a recent refacto of the LRS query parameter used in Ralph backend was applied on the API router to parse query parameters.

Proposal

An improvement would be to reuse the RalphStatementsQuery model to specify the signature of the LRS query statements resource router methods. This would be beneficial to avoid redefinition and respecification for the same data and reduce typing errors