feat: Bind data using headers as source

[noseglid]

Currently, echo supports binding data from query, path or body.
Sometimes we need to read bind data from headers. It would be nice to
automatically bind those using the bindData func, which is already
well prepared to accept http.Header.

I didn't add this to the Bind func, so this will not happen
automatically. Main reason is backwards compatability. It might be
confusing if variables are bound from headers when upgrading, and might
even have become a security issue as pointed out in #1670.

[noseglid]

I realize we should add documentation over this seeing as this is a new feature and all. But I wanted to get the PR up here to see if this is something you'd be willing to accept. And if so, we can discuss next steps.

[codecov]

Codecov Report

Merging #1866 (11d6bf8) into master (6430665) will increase coverage by 0.64%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1866      +/-   ##
==========================================
+ Coverage   89.57%   90.22%   +0.64%     
==========================================
  Files          31       31              
  Lines        2735     2773      +38     
==========================================
+ Hits         2450     2502      +52     
+ Misses        184      173      -11     
+ Partials      101       98       -3     

Impacted Files	Coverage Δ
bind.go	89.41% <100.00%> (+0.52%)	⬆️
middleware/timeout.go	100.00% <0.00%> (ø)
middleware/jwt.go	79.80% <0.00%> (+1.91%)	⬆️
middleware/static.go	70.00% <0.00%> (+2.83%)	⬆️
middleware/key_auth.go	96.55% <0.00%> (+29.88%)	⬆️

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[aldas]

LGTM

[noseglid]

Anything else you expect from me in this?

[lammel]

Anything else you expect from me in this?

Could you open a PR in https://github.com/labstack/echox/pulls to update the documentation please.
Nice work. We'll merge when the docs PR is linked.

[noseglid]

labstack/echox#210

[liaohongxing]

func hello(c echo.Context) error {
	c.Request().Header.Set("id", "1")

	input := new(struct {
		ID int `header:"id"`
	})

	if err := c.Bind(input); err != nil {
		return err
	}

	fmt.Println(input)

	return c.JSON(http.StatusOK, input)
}

result: {"ID":0} ,c.Bind lacks support

[aldas]

Yes, c.Bind() does not bind header. To bind headers you would need to use

		if err := (&echo.DefaultBinder{}).BindHeaders(c, input); err != nil {
			return err
		}

This is intentional as original author points out #1866 (comment)

[tunhuit]

Should we add this feature to Bind() in Echo v5 or next release? It should have some notice about breaking compatibility.