Provide oauth support as implemented in SAP Commerce cloud

[a-thaler]

Description
To provide the same experience when it comes to secure access, the commerce mock must be enhanced to support the authentication mechanisms used in SAP Commerce cloud.

Referring to the example, https://github.com/kyma-project/examples/tree/master/call-ec

following OAuth related URLs should be supported. But I believe there could be more stuff as the example seems to be outdated.

REACT_APP_OAUTH2_ISSUER=https://commerce.gaurav-demo-call-ec.cluster.extend.sap.cx/authorizationserver
REACT_APP_OAUTH2_JWKS_URI= https://commerce.gaurav-demo-call-ec.cluster.extend.sap.cx/authorizationserver/.well-known/jwks.json
REACT_APP_OAUTH2_AUTHORIZE_URL=https://commerce.gaurav-demo-call-ec.cluster.extend.sap.cx/authorizationserver/oauth/authorize