Quality arguments to Accept header should default to 1.0

[hiddewie]

This PR ensures that Accept headers with mime types without a given quality value, are parsed as having a quality value of 1.0.

The current value for mime types without a quality value is 0.0 (nil.to_f).

From the HTTP specification (RFC 9110), https://www.rfc-editor.org/rfc/rfc9110.html#name-accept and https://www.rfc-editor.org/rfc/rfc9110.html#name-quality-values:

The weight is normalized to a real number in the range 0 through 1, where 0.001 is the least preferred and 1 is the most preferred; a value of 0 means "not acceptable". If no "q" parameter is present, the default weight is 1.

[dblock]

Add a test that with nil, 0.0, and invalid, too?

[hiddewie]

Thanks for the review. I changed the parsing to include all q=... values. This will try to parse every value to a floating point number. Invalid (textual) values will be parsed as 0.0. The empty q value will become a default quality of 1.0 which looks like a fine behaviour for me.

[dblock]

Add to CHANGELOG and this is good to go!

[hiddewie]

Thanks, done!

[dblock]

One more, should we also document this in README? We don't need to explain the entire purpose of q, but maybe call it out in https://github.com/ruby-grape/grape#header with an example that chooses JSON over XML? Maybe something like this?

"Grape will evaluate the relative quality preference included in Accept headers and default to a quality of 1.0 when omitted. In the following example a Grape API that supports XML and JSON in that order will return JSON."

curl ... -H "Accept: text/xml;q=0.8, application/json;q=0.9"

[hiddewie]

Sounds good, done in 7a6cefc!

[dblock]

Merged, nice work, thanks for hanging in here with me!