test: add CLI and client mock test

[kemingy]

• serde
• CLI read-stdin/write-file
• save the response to local files
• config

[tddschn]

How do you want to test config?

Read random config with EnvConfig and check if EnvConfig is initialized with correct values?

[kemingy]

How do you want to test config?

Read random config with EnvConfig and check if EnvConfig is initialized with correct values?

Check if it can read from env correctly.