GTFS download from URL: send a User-Agent

[derhuerst]

Describe the problem

As someone hosting (a) GTFS(s), I would like to see in my access logs which and how many requests come from the GTFS Validator, e.g. to gain insights into if/how the feed(s) are being validated, or to provide a more generous bandwidth quota.

Proposed solution

I propose to let the GTFS Validator send a User-Agent header with its requests.

Alternatives you've considered

No response

Additional context

According to the User-Agent section in RFC 9110 (HTTP Semantics), User-Agent should

contain[s] information about the user agent originating the request, which is often used by servers to help identify the scope of reported interoperability problems, to work around or tailor responses to avoid particular user agent limitations, and for analytics regarding browser or operating system use. A user agent SHOULD send a User-Agent header field in each request unless specifically configured not to do so.
[…]
The User-Agent field value consists of one or more product identifiers, […], which together identify the user agent software and its significant subproducts. […] Each product identifier consists of a name and optional version.

It is also quite common to include a URL to the software's website or code repository, to let people contact the software's authors more conveniently.

[davidgamez]

Hi @derhuerst, as part of #1633, we're including the user-agent header in outgoing requests. To illustrate the expected formatting, this is an example, User-Agent: MobilityData GTFS-Validator/4.2.1 (Java 17.0.6). We welcome any feedback you may have.

[derhuerst]

Sounds good!