Eset protect oauth2 cleanup

[ezzamo]

Proposed commit message

eset_protect: remove unsupported OAuth client_id/client_secret fields

WHAT

This PR updates the eset_protect integration OAuth configuration to align with the current ESET Connect API specification for /oauth/token.

• Removes client.id and client.secret from the auth.oauth2 configuration in the CEL inputs.
• Keeps the existing authentication flow intact (password grant to obtain tokens, and refresh token grant for renewal).

WHY

The ESET Connect API Swagger documentation for /oauth/token specifies the request body for supported grant types (password and refresh_token). In that specification, the request body parameters no longer includes client_id or client_secret as it is fully deprecated.

The integration currently includes client.id and client.secret fields (set to empty strings). These fields are no longer supported by the published specification and are therefore unnecessary. Keeping them in the integration configuration is misleading during troubleshooting (it suggests the API expects these client credentials).

References:

• Authentication (OAuth token) Swagger: https://eu.esetconnect.eset.systems/swagger/?urls.primaryName=Authentication#/OAuth/OAuth_Token
• #9600

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.
• I have verified that any added dashboard complies with Kibana's Dashboard good practices.

How to test this PR locally

From the integrations repo:

• cd packages/eset_protect
• elastic-package lint
• elastic-package build

upload it through kibana

Related issues

• N/A

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)