Same styles used for eIDAS and SPID access buttons

[mauromol]

The CSS file for the eIDAS access button present here contains declarations about styles named as italia-it-button[-*].
The same style names are used for the SPID SP access button.

These final result is that if you want to put the SPID access button and the eIDAS access button on the same page, as per AgID guidelines, and you then import both CSS files in your HTML page, styles from the eIDAS CSS will override those from the SPID CSS.
The most visible result is that the SPID access button will have rounded corners, instead of straight ones.

See, for instance:

eidas-italian-node/eidas-button/src/production/css/eidas-sp-access-button.css

Line 2 in b6a6454

.italia-it-button {

which is the same style used at:
https://github.com/italia/spid-sp-access-button/blob/2fe1955ac8d267b7399d1dca3ed92ed05c5fb030/src/production/spid-sp-access-button.html#L18
however it brings border-radius: 15px.

Possibile solutions:

• rename the italia-it-button[-*] styles in either this eIDAS access button or SPID access button (I would say it's better to change them here)
• limit the scope of the italia-it-button[-*] styles with a CSS descendant selector in both projects so that they are applied only when those styles appear within a HTML container with a unique id or style (but this may perhaps also require changes to the HTML pages... I've not investigated further)