Feat: support for authentication

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Description

• Extend Java SDK protocol with AuthenticationRequest / AuthenticationResponse messages.
• Make authentication callback configuration in SessionOptions.
• Enable the default ANONYMOUS authentication for docker bmqbrkr.tsk ITs and bmq-examples.
• Extend connection FSM with new AUTHENTICATING state, handle authentication events.

Design decisions

Authentication auto enablement

I decided not to add ANONYMOUS authentication callback to the default SessionOptions because it breaks a half of the existing tests. We have 2 types of ITs in SDK: the ones with real broker and the ones with mock broker simulator. The real broker works fine, the mocks require not-trivial updating. I will do it in the next PR.

AuthnCredential callback

a. C++ mirror (Optional, StringBuilder):

        final SessionOptions sessionOptions =
                SessionOptions.builder()
                        .setBrokerUri(URI.create(brokerUri))
                        .setAuthnCredentialCb(
                                error ->
                                        Optional.of(
                                                AuthnCredential.builder()
                                                        .setMechanism("ANONYMOUS")
                                                        .setData(new byte[0])
                                                        .build()))
                        .build();

Java already supports nullable references so there is no real need to use Optional, we can just return null. Also it is not very convenient to provide a string builder to the call.

b. Builder variant:

        final SessionOptions sessionOptions =
                SessionOptions.builder()
                        .setBrokerUri(URI.create(brokerUri))
                        .setAuthnCredentialCb(
                                () ->
                                        AuthnCredentialResult.success(
                                                AuthnCredential.builder()
                                                        .setMechanism("ANONYMOUS")
                                                        .setData(new byte[0])
                                                        .build()))
                        .build();

AuthnCredentialResult holds either a valid credential or an error message.

c. Hidden builder variant - implemented:

        final SessionOptions sessionOptions =
                SessionOptions.builder()
                        .setBrokerUri(URI.create(brokerUri))
                        .setAuthnCredentialCb(
                                () ->
                                        AuthnCredentialResult.success("ANONYMOUS", new byte[0]))
                        .build();

The protocol is fixed, so we can rely on the fact that we will always have a mechanism and a data. It is unlikely that we will be able to extend the protocol easily. So we can hide the AuthnCredential builder and make AuthnCredentialResult build easier.

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We can assume that missing setData means empty byte array new byte[0], but in most cases we expect to have something in data, so this API simplification is not useful for the future use.

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This callback is more convenient than C++ one.
In C++, the callback is:

typedef bsl::function<bsl::optional<AuthnCredential>(bsl::ostream& error)>
        AuthnCredentialCb;

In Java, we don't want to provide a string builder arg when we can just return a "variant" type that is either a correct result or error message.

Maybe we can update the C++ implementation to match this.

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Changes here:

1. Added a new row /* s2 AUTHENTICATING */. As a result, all values in this table that are > 2 got incremented by 1. Value 2 was for NEGOTIATING and now it is pointing to AUTHENTICATING state.

2. In each existing row, 3 values added to the end. These values are for authentication events. We do not expect these events in any state except AUTHENTICATING so we do not change state if we observe them in s0-s1, s3-s7.

3. We go from AUTHENTICATING to NEGOTIATING only on AUTHENTICATION_RESPONSE

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AuthenticationResponse is constructed by Gson during deserialization with Field.set, there is no need to provide any specific APIs to set fields such as setters or constructor with arguments

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AuthenticationRequest is constructed in SDK.
We provide only a constructor with arguments and make it immutable after construction

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If decoding fails, we will log the error and still pass this event to FSM.
FSM handler TcpBrokerConnection::handleAuthenticationResponse will see the null authnChoice and will send AUTHENTICATION_FAILURE to FSM.

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This will make container ITs run with authn