Fix checkout-cart-url flag

[alvaro-shopify]

WHY are these changes introduced?

Running the dev command with the flag checkout-cart-url is not working with checkout ui extensions generated from the new template. The product shown when you visit the checkout extension preview url is different to the one you set in the flag

There are some issues to dev checkout ui extensions in spin because an error is returned from the admin api when the product variant is fetched. Using the flag is not working as workaround

WHAT is this pull request doing?

• Remove the old method that built the url. It was receiving the cart url flag value and in case there are no checkout_ui_extension type it returned undefined as the cart url, so the flag value is lost. New checkout ui extensions have the generic ui-extension type, so we should filter them using the method shouldFetchCartUrl which applies to the old and new checkout ui extensions
• Remove duplicate call to the cart url build method inside the execution of the dev ui process.

How to test your changes?

Test 1

• Run the dev command with one product variant

p shopify app dev --path /path/to/your/app  --checkout-cart-url /cart/43823180349462:1

• Visit the checkout ui extension preview url and the product variant displayed in the cart should match the one you set in the flag

Test 2

• Run the dev command without the flag

p shopify app dev --path /path/to/your/app 

• Visit the checkout ui extension preview url and you should see a random product from your store

Post-release steps

Measuring impact

How do we know this change was effective? Please choose one:

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix
• Existing analytics will cater for this addition
• PR includes analytics changes to measure impact

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've made sure that any changes to dev or deploy have been reflected in the internal flowchart.

[github-actions]

We detected some changes at either packages/*/src or packages/cli-kit/assets/cli-ruby/** and there are no updates in the .changeset.
If the changes are user-facing, run "pnpm changeset add" to track your changes and include them in the next release CHANGELOG.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	74% (+0.07% 🔼)	6079/8215
🟡	Branches	71.2% (+0.07% 🔼)	2971/4173
🟡	Functions	72.53% (+0.07% 🔼)	1550/2137
🟡	Lines	75.3% (+0.05% 🔼)	5767/7659

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟡	... / previewable-extension.ts	77.78% (+7.19% 🔼)	50%	66.67% (-13.33% 🔻)	75% (+5.77% 🔼)

Test suite run success

1441 tests passing in 673 suites.

Report generated by 🧪jest coverage report action from 3107ce4

[isaacroldan]

Good catch 👌