Add "enterprise" license OperationMode

[tvernum]

Elasticsearch supports the "enterprise" type stack license, but internally it maps that to the "platinum" operation mode.

We should create an explicit "enterprise" operating mode so that it is possible for new functionality to be tied to this license type.

Relates: #48510

[elasticmachine]

Pinging @elastic/es-security (:Security/License)

[tvernum]

I think it might be time to do a refactor of XPackLicenseState when we do this. There are a lot of methods there, many of which are tied to explicit modes.

It might be better to replace the body of each of those isXyzAllowed() methods with a call to something common e.g.

    public boolean isSqlAllowed() {
        return checkMinimumLicense(OperationMode.BASIC);
    }

    public boolean isJdbcAllowed() {
        return checkMinimumLicense(OperationMode.PLATINUM);
    }

    private boolean checkMinimumLicense(OperationMode mode) {
        return checkMinimumLicense(mode, true);
    }
  
    private synchronized boolean checkMinimumLicense(OperationMode minimumMode, boolean allowTrial) {
        Status localStatus = status;
        if (localStatus.active == false ) {
            return false;
        }
        if (allowTrial && localStatus.mode == OperationMode.TRIAL) {
            return true;
        }
        return localStatus.mode >= minimumMode;
    }

[ywangd]

Should every one of these methods check status.active == true? Some of them don't, e.g. isApiKeyServiceAllowed? If refactored, the active check will be applied. Or should we make exception for them?

[tvernum]

Good point.
A few features, like security (and therefore API Keys) are intended to be permitted even if the license expires (active == false). We don't want to turn off security when a license expires, and if security is on, then you need to be able to authenticate (via any authentication method).

So, we need an exception.

[ywangd]

There is also a MISSING operation mode which is not handled in every case. For an example, the XPackLicenseState#isSecurityEnabled handles it as default, i.e. same as gold or platinum. Is this an issue?

[tvernum]

MISSING will mostly (fully?) go away with #45022
If it stays, I think we may need to look at it on a case-by-case basis but for non-security we could treat it like BASIC
For security we probably want to continue to treat it like PLATINUM so that a license problem doesn't break security.

[ywangd]

Cool makes sense. Currently there is a bit inconsistency between code and javadocs. For an example, isEnrichAllowed only check whether a license is active. But its javadocs says all license types except MISSING. I lean towards removing the line in javadocs. Sounds reasonable to you?

[tvernum]

Sounds reasonable to you?

Yes. If the implementation of isEnrichAllowed is clean (e.g. checkMinimumLicense(OperationMode.BASIC);) then I don't think it really needs Javadoc.

The purpose of the method is clear from the name. The behaviour is clear from the implementation. What more does the Javadoc add?

[ywangd]

What more does the Javadoc add?

Nothing. Code should be treated as the ultimate reference. So I'll delete the doc line as it adds nothings but confusion. Thanks.