Use rust `mockall` lib to facilitate the creation of mocks

[lorenzoberts]

Context:

With the mockall lib it is very easy to create a mock for any struct or trait. It avoids the creation of separated structs just for testing.

Proposal:

[Your proposal of code change]
The struct FakeLoreAPIClient, for example, could be replaced by a real mock for the lore api client

Setup:

• Project branch: unstable
• Project commit hash: 7379a9a
• rustc version: rustc 1.80.1 (3f5fd8dd4 2024-08-06)
• cargo version: cargo 1.80.1 (376290515 2024-07-16)