Add a basic set of KorvServer tests

[tryexceptpass]

Using pytest as the test framework, add the basic tests that verify a server instance:

• Instantiate KorvServer without errors using newly generated SSH keys.
• GET routes execute correctly and respond with valid JSON.
• STORE routes execute correctly and respond with valid JSON.
• UPDATE routes execute correctly and respond with valid JSON.
• DELETE routes execute correctly and respond with valid JSON.
• Verify it's not possible to connect with the wrong SSH key.