Add custom user agent header for metro lisboa feed

[ianktc]

Summary:

Add custom User-Agent header=MobilityDatabaseAgent for Metro Lisboa. I verified that without any header, the response using python request lib is 403 Forbidden. When using our new custom user agent (MobilityDatabaseAgent) we're able to get a 200 response.

MobilityData/mobility-database-catalogs#1693

Liquibase Changes:

• Added a new migration, add_metro_lisboa_header.sql, to insert a custom User-Agent header override for Byron Bay Express (tld-716): (liquibase/changes/add_metro_lisboa_header.sql)
• Updated the main Liquibase changelog (changelog.xml) to include the new hotfix migration, ensuring it is applied in the correct order. (liquibase/changelog.xml)

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• Run the unit tests with ./scripts/api-tests.sh to make sure you didn't break anything
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