* Add `IntegrationPattern` contract to implement on the target components
which represent particular EIP
* Add `IntegrationPatternType` with an internal `IntegrationPatternCategory`
to return from the component implementing `IntegrationPattern`
* Parse `IntegrationPatternType` in the `IntegrationNode` for potential
use on the UI for drawing a particular icon
* More pattern representations
* Clean up Checkstyle
* Fix JavaDocs
* Add `integrationPatternCategory` assertion into the `IntegrationGraphServerTests`
* Add more IntegrationPattern implementations
* Provide some delegation and overriding logic whenever we have
components wrapping
* Fix unused imports
* Add `inbound_gateway` pattern indicator
* Add conditional on `expectReply` to indicate a component as an
`IntegrationPatternType.outbound_channel_adapter` or
`IntegrationPatternType.outbound_gateway`
* Make some code clean up in affected classes
* Add a `gateway` type for `@MessagingGateway`
* Comment the reason for `outbound_gateway` type in the `AbstractReplyProducingMessageHandler`
* Bump `IntegrationGraphServer.GRAPH_VERSION`
* Add new attributes into graph sample in the `graph.adoc`
* Document an `IntegrationPattern`
* Apply changes for version 5.3
* Rebased into `5.3-WIP`
* Add a `whats-new.adoc` note about an `IntegrationPattern`
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