3783589 - authentication fails for edge integration cell using custom IdP technical user with error "your SAP BTP user credentials are not valid" — SAP integration suite

• Following the setup for edge integration cell, establishing the connection with a technical user via custom IdP is not possible.
• Manual user authentication on Identity Authentication Service (IAS) works.
• Connection test authentication is unsuccessful.
• Error message: "Your SAP Business Technology Platform user credentials are not valid. Please update your credentials."
• The password grant type is already configured in XSUAA 
• The following XSUAA error can be found:
  • org.cloudfoundry.identity.uaa.oauth.common.exceptions.InvalidClientException
    Message:

    {"error":"unsupported_grant_type","error_description":"Invalid grant_type parameter value, allowed grant_types: refresh_token, client_credentials, authorization_code, urn:ietf:params:oauth:grant-type:jwt-bearer"}

• Product: SAP Integration Suite
• OIDC/OAuth2 component in SAP Cloud Identity Services
• XSUAA (password grant flow)
• Edge Integration Cell / Edge Lifecycle Management

edge integration cell, custom idp, technical user, password grant, unsupported_grant_type, xsuaa, noninteractive logon, sap.custom, login_hint, identity authentication, oauth2 password, connection test failed, default idp, shadow users, grant types , KBA , BC-IAM-OID , OIDC/OAUTH2 component in SAP Cloud Identity Services , Problem