bug: Add / to graphql validation endpoint

[sirugh]

Description

The graphql validation endpoint we added in #1004 did not have a /. Since we don't mandate that the MAGENTO_BACKEND_URL end with a forward slash we should add one here to be safe.

Motivation and Context

$ yarn run download-schema && graphql validate-magento-pwa-queries --project venia
$ graphql get-schema --project venia
⚠ request to https://release-dev-231-npzdaky-zddsyhrdimyra.us-4.magentosite.cloudgraphql failed, reason: getaddrinfo ENOTFOUND release-dev-231-npzdaky-zddsyhrdimyra.us-4.magentosite.cloudgraphql release-dev-231-npzdaky-zddsyhrdimyra.us-4.magentosite.cloudgraphql:443
Validating GraphQL queries in venia project...
✖ An error occurred:
Could not find a schema at lastCachedGraphQLSchema.json.
 Run `graphql get-schema --project venia` to download the schema before running validate-magento-pwa-queries.
error Command failed with exit code 1.

Verification

To verify, set the MAGENT_BACKEND_URL in your .env to something without a / like MAGENTO_BACKEND_URL="https://release-dev-231-npzdaky-zddsyhrdimyra.us-4.magentosite.cloud"

Then from root run yarn run validate-queries. It should fail.
Then check out this PR and run it again, and it should pass.

How Has This Been Tested?

Above verification. Also tested with url ending with /.

Screenshots (if appropriate):

Proposed Labels for Change Type/Package

Checklist:

• I have read the CONTRIBUTING document.
• I have linked an issue to this PR.
• I have indicated the change type and relevant package(s).
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All CI checks are green (linting, build/deploy, etc).
• At least one core contributor has approved this PR.

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[zetlen]

This is a good addition, but it's a reminder to me that we need proper URI construction as part of UPWARD.

[sirugh]

Yea I felt like its sort of papering over an issue but // is better than nothing :)

[coveralls]

Coverage remained the same at 76.917% when pulling 9c150d9 on sirugh_fix_graphql_check into 4b82402 on develop.

[brendanfalkowski]

Just tested this out, and yarn run build fails for me on the following:

⚠ request to https://m2pwa.test//graphql failed, reason: unable to verify the first certificate

Opening https://m2pwa.test//graphql and https://m2pwa.test/graphql in the browser, both lead to this:

I tried changing .env to contain or omit the trailing slash, but no effect.

I'm working off "pwastudio :: develop" branch. Any ideas?

[sirugh]

@brendanfalkowski I've not seen the certificate error before. I think that is unrelated to this fix. Open an issue please!