[Feature] Manage request header

[gmorel]

Pain Point

We are able to deal with

• Raw
• GET
• POST

We should be able to map and validate header too.

TODO

• Implement Request/PureHeaderValueValidator
  • mustBeString
• Implement Request/PragmaticHeaderValueValidator
  • mustBeUuid
• Manage Header in AbstractPureCommandResolver
  • Extract attribute + query into a PureRequestValidator in order to ease further enhancement
    • Try to avoid train wreck
    • $this->requestValidator->queryStringValueValidator->mustBeString
• Manage Header in AbstractPragmaticCommandResolver
  • Extract attribute + query into a PragmaticRequestValidator in order to ease further enhancement
    • Try to avoid train wreck
    • $this->requestValidator->queryStringValueValidator->mustBeUuid