[CAT-92] DatabaseClient 모듈 추가 · Nexters/Mohanyang-iOS@8383f3a

Force casts should be avoided (force_cast)

Implicitly unwrapped optionals should be avoided when possible (implicitly_unwrapped_optional)

Returning Void in a function declaration is redundant (redundant_void_return)

Files should not contain leading whitespace (leading_whitespace)

Type name 'T' should be between 3 and 40 characters long (type_name)

Files should have a single trailing newline (trailing_newline)

Force unwrapping should be avoided (force_unwrapping)

Force unwrapping should be avoided (force_unwrapping)

Closure parameters should be on the same line as opening brace (closure_parameter_position)

Closure parameters should be on the same line as opening brace (closure_parameter_position)

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