Separate 0x API from DIVA API

[Walodja1987]

Context

The codebase for this project is derived from 0x's API. In order to streamline development, the EIP712 offer functionality specific to DIVA was integrated into the existing 0x API codebase. However, due to the unavailability of 0x Protocol on certain networks (e.g., Gnosis), we are unable to provide the API service for DIVA offers on Gnosis.

To address this issue, it is necessary to decouple the DIVA functionality from the 0x API codebase. By separating the two components, we can ensure compatibility with networks such as Gnosis and provide the intended functionality for DIVA offers on these platforms.