Loosen API for form inputs?

[adbehahn]

Code of conduct

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Description of issue

sp-checkbox doesn't expose a "name" attribute in its API:

            <input
                id="input"
                aria-labelledby="label"
                type="checkbox"
                .checked=${this.checked}
                @change=${this.handleChange}
            />

I was wondering if either 1) name could be added to the API or 2) all properties that aren't used exclusively by the wrapping component could be passed through to the input.

Same thought applies to all inputs wrapped by Spectrum.

As a coder, a goal would be to leverage built-in Javascript API's and therefore be able to write simpler and less risky code, such as:

const formData = new FormData(form);

[Westbrook]

Notes:

• this likely would benefit from https://github.com/open-wc/form-participation
• ☝🏼 relies (correctly) on elementInternals which is not yet available everywhere, but can be polyfilled via: https://www.npmjs.com/package/element-internals-polyfill
• attachInternals also opens up attribute free (sans polyfill) aria value application, which @joekukish is interested in and relates to [Docs] Outline sprouted attributes/children/etc that may impact snapshot testing #1742