guard

Add the following extensions methods for dictionaries:

var dictionary = new Dictionary<string, string>
{
    ["key1"] = "value1",
    ["key2"] = "value2",
};

dictionary.Throw().IfContainsKey("key1");
dictionary.Throw().IfNotContainsKey("key3");

And the corresponding dictionary properties extension methods:

var dictionary = new Dictionary<string, string

Would be nice to rename/deprecate method name 'getIpFromRequest' and add something like getKeyFromRequest, because custom guards may not use IP as key, so such method name a bit misleading.

Instead of writing tg.throwIf(tg.isNot(tg.isString)), it would be nicer to write tg.throwUnless(tg.isString).