Add tests and add secrets for CI workflow

[GevinHasmitha]

Purpose

Added tests cases for fhirr4-medications-api-service.
Added epic github secret variables for CI workflow (need to populate them in the WSO2 repository for it to work, also should have enough scope or the tests will fail)

Populating the Secrets

Have the following as the github secret names

EPIC_FHIR_SERVER_URL
EPIC_FHIR_SERVER_TOKEN_URL
EPIC_FHIR_APP_CLIENT_ID
EPIC_FHIR_APP_PRIVATE_KEY_FILE

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