Adds Shop Login Button liquid drop provider on login template

[QuintonC]

PR Summary:

Adds a sign in with Shop button to the Classic Customer Accounts login form. This includes the ability for the button to be hidden by merchants who do not wish to show the shop login button.

What approach did you take?

Extended on the existing implementation in main-login.liquid by utilizing our Shop login button liquid drop with additional settings which allow the button to be hidden.

I've also added translation strings for the settings and the separator (or) text.

Additionally, the login button inherits the border radii set by merchants via the CSS variable.

Visual impact on existing themes

Merchants who are using Dawn or other OS2.0 themes will see an added Sign in with Shop button on their classic customer accounts page.

It can be hidden by merchants if desired by toggling the "Hide button" setting.

Hide Button setting

Testing steps/scenarios

• Navigate to the test store (link)
• Go to /accounts/login
• Click the button, and sign in using a Shop account. If you do not have one, you can create one through the sign in with Shop flow.
• After signing in, refresh the page
  • This is only a temporary step until we patch the classic customer accounts script to update the button added by this change rather than appending a hidden button the bottom of the page.
• You should be authenticated to your customer account

Demo links

• Store

Checklist

• Added PR summary for release notes
• Requested review from UX (Only for changes that are affecting the experience or perceivable visual details)
• Created a ticket for the help.shopify.com documentation team about updates to theme settings. (Internal-only task)
• Followed theme code principles
• Linted with Theme Check
• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility

[melissaperreault]

Hey team! Made a few comments that I'll regroup below:

• Order of setting can be revised: moving up the checkbox setting will bring coherence in how other sections places the padding settings always at the very end of the sidebar.
• We don't need a header if the setting is already explicit. Also reduces noise for merchants.
• Have the setting label use a positive form