CORS middleware

[juancwu]

Checklist

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Description

CORS middleware that is configured differently based on app environment by default. Make the server code cleaner.

Linked Issues

• Closes [BE Feat] Create CORS middleware #212

Type of Change

Please delete options that are not relevant:

• 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 not work as expected).
• This change requires a documentation update.

Testing

• Tested the get config based on app env function
• Tested headers that should exists in a request when CORS is enabled

[AmirAgassi]

should use env variable for URLs

[AmirAgassi]

lgtm

[AmirAgassi]

still lgtm