Refactor Allow header
Rename variable
Refactor Age header
Refactor Accept-Ranges header renaming a variable
Refactor Content-Language header
Refactor ContentLenght
Some getters for ContentType
Some validations and refactorings for Date
Refactor Date class
Apply same refactoring for other date headers
Create Abstracts\TimeHeader to remove code duplication
Create getDateTime and getTimestamp methods
Create constant Pragma::NO_CACHE
Refactor RetryAfter making it a TimeHeader
Remove old exception
Refactor StrictTransportSecurity