[#225] Bind identity provider configs through the DS bind methods

[vharseko]

Fixes #225

Problem

IdentityProviderService declared its @Reference to IdentityProviderConfig on a Map<String, List<IdentityProviderConfig>> field. Declarative Services cannot inject that type, so SCR rejected the reference (Field identityProviders ... has unsupported type java.util.Map) and bindIdentityProviderConfig / unbindIdentityProviderConfig were never called. As a result /identityProviders always answered {"providers":[]}, no OPENID_CONNECT / OAUTH auth module was generated, and the social self-service stage received no providers.

The annotations were moved onto the fields in 5aa45c8 (the Felix SCR → OSGi DS migration). The same thing happened in AuthenticationService: its @Reference to IdentityProviderService is on the field, and because the field type is valid, SCR injects it without logging anything. bindIdentityProviderService, which registers the provider listener, was never called either, so provider changes never reached the authentication filter.

Changes

• IdentityProviderService: the reference is declared on bindIdentityProviderConfig, with an explicit unbind and the same reference name identityProviders. Providers are added atomically (computeIfAbsent + CopyOnWriteArrayList). getIdentityProviderByType now returns an empty list for a type with no bound provider. Before this change that path could not be reached; with providers bound it would have thrown an NPE.
• AuthenticationService: the reference is declared on bindIdentityProviderService, and unbindIdentityProviderService now takes the service argument that DS requires. Both methods rebuild the social auth modules. This does nothing before activation, and covers IdentityProviderService arriving after AuthenticationService has already activated.

Generated descriptors:

<reference name="identityProviders" cardinality="0..n" policy="dynamic" interface="org.forgerock.openidm.idp.impl.IdentityProviderConfig" bind="bindIdentityProviderConfig" unbind="unbindIdentityProviderConfig"/>
<reference name="identityProviderService" cardinality="0..1" policy="dynamic" interface="org.forgerock.openidm.idp.impl.IdentityProviderService" bind="bindIdentityProviderService" unbind="unbindIdentityProviderService"/>

Tests

• IdentityProviderServiceTest: added tests for a lookup by a type with no bound providers, and for unbind (the provider is removed and listeners are notified).
• AuthenticationServiceTest: added tests that bind registers the listener and that unbind unregisters it and stops injecting providers. The existing tests now call setConfig after bind, which is the order SCR uses (bind before activate).
• The existing tests called bind* directly and so never exercised the SCR wiring. The descriptors above were checked in the built jars.

Note: #207 touches the same line in getIdentityProviderByType, so whichever PR merges second will get a trivial conflict.