Added types to private functions, improved readability, shouldCheckProxyHeaders as separate function

[satalaondrej]

Hello,

I am proposing some minor improvements/changes

• added argument and return types to private functions parseWildcard, parseCidr, getFirstIpAddressFromHeader
• improved isValidIpAddress function readability
• moved determining whether proxy headers should be checked to separate shouldCheckProxyHeaders function

[akrabat]

Replaced by #43 as we need to pass CI.