Use standards-compliant value in User-Agent HTTP header field sent by Composer installer

[Nico Roeser]

Currently, the Composer installer identifies with an incorrect value in the User-Agent header field when it sends HTTP requests.

Spaces are not allowed, and the version is separated from the user agent product identifier by a slash. This is explained in RFC 7231 (“Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content”) section 5.5.3 (“User-Agent”). (token is defined in RFC 7230 (“Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing”) section 3.2.6 (“Field Value Components”).)

[Jordi Boggiano]

Ah thanks, wasn't aware of that restriction.

[Jordi Boggiano]

cc @johnstevenson btw just FYI

[John Stevenson]

@Seldaek Thanks.