OpenAPI Extension Annotations

[RoshniNaveenaS]

In this PR , we will be supporting @OpenAPI.Extensions in three levels:

1. Schema Level
2. Entity level
3. Operation level ( action or function)

Example:
In CDS:

In OpenAPI:
1extension.openapi3.json

Link to list of possible annotations : https://github.com/SAP/openapi-specification/tree/main/sap-schemas/v3.0

List of special handling:
If other values/ fields are given for the extensions mentioned below, then

Extension	Allowed Values/ Fields
x-sap-compliance-level	allowedValues: ["sap:base:v1", "sap:core:v1", "sap:core:v2" ]
x-sap-api-type	allowedValues: [ "ODATA", "ODATAV4", "REST" , "SOAP"]
x-sap-direction	allowedValues: ["inbound", "outbound", "mixed"] , default : "inbound"
x-sap-dpp-entity-semantics	allowedValues: ["sap:DataSubject", "sap:DataSubjectDetails", "sap:Other"]
x-sap-dpp-field-semantics	allowedValues: ["sap:DataSubjectID", "sap:ConsentID", "sap:PurposeID", "sap:ContractRelatedID", "sap:LegalEntityID", "sap:DataControllerID", "sap:UserID", "sap:EndOfBusinessDate", "sap:BlockingDate", "sap:EndOfRetentionDate"]
------	Schema --------
x-sap-stateInfo	['state', 'deprecationDate', 'decomissionedDate', 'link']
x-sap-ext-overview	['name', 'values']
x-sap-deprecated-operation	['deprecationDate', 'successorOperationRef', "successorOperationId"]
x-sap-odm-semantic-key	['name', 'values']

[jeevitha011]

lgtm