refactored env vars into new constants file

[bklaing2]

Purpose

There is a common pattern repeated throughout the code when using some ENV vars. For example:

const pageUrl =
    process.env.NEXT_PUBLIC_API_URL === 'https://api.datacite.org'
      ? 'https://commons.datacite.org/doi.org/' + data.work.doi
      : 'https://commons.stage.datacite.org/doi.org/' + data.work.doi

closes: Add github issue that originated this PR

Approach

This PR refactors most environment variables into a constants.ts file. The updated example is now:

const pageUrl = `${COMMONS_URL}/doi.org/${data.work.doi}`

Open Questions and Pre-Merge TODOs

• Many of the variables in constants.ts rely on checking if process.env.NEXT_PUBLIC_API_URL === 'https://api.datacite.org' to determine if they should use the prod or stage version of their URL. We may consider using the NODE_ENV variable instead.
• Building on the previous point, most of our ENV variables aren't actually secrets and are already hardcoded as fallbacks anyways. If we use the NODE_ENV to determine which URL to point to then we can remove most of the ENV vars.

Learning

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• New feature (non-breaking change which adds functionality)

• Breaking change (fix or feature that would cause existing functionality to change)

Reviewer, please remember our guidelines:

• Be humble in the language and feedback you give, ask don't tell.
• Consider using positive language as opposed to neutral when offering feedback. This is to avoid the negative bias that can occur with neutral language appearing negative.
• Offer suggestions on how to improve code e.g. simplification or expanding clarity.
• Ensure you give reasons for the changes you are proposing.

[cypress]

akita    Run #1575

Run Properties:   Passed #1575  •  ad0e5898e3 ℹ️: Merge 1348c022b9a07756dd8522cc793e9599baac99d0 into 48e76ac7ce8e31f87d140de2c51e...

Project	akita
Branch Review	refactor-env-vars
Run status	Passed #1575
Run duration	01m 33s
Commit	ad0e5898e3 ℹ️: Merge 1348c022b9a07756dd8522cc793e9599baac99d0 into 48e76ac7ce8e31f87d140de2c51e...
Committer	Bryceson Laing
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	3
Skipped	0
Passing	50
View all changes introduced in this branch ↗︎