sharing: created new entity share package (justtrackio#895)

kafka: Introduce input and output;

to add support for head-of-line-blocking (HOL) inputs like Kafka,
the AcknowledgeableInput interface and ack logic has been adapted.

this affects inputs, as the consumer will always call the
underyling input.Ack(bool), even on failure, but with a boolean flag
indicating success/failure.

introduced kafka features:
    - Implement input and output.
    - Implement offset management and batching through OffsetManager.

[funk]: retain order during Uniq;

test: add response templating to wiremock; (justtrackio#907)

introduce prometheus metrics

    - apiserver: expose metrics endpoint
    - metric: add prometheus metric writer
    - examples: add prometheus metrics example

kernel: refactored the kernel interface and split creation and execut…

…ion;

With this change we're splitting the creation and execution of a kernel into multiple parts.

This introduces mainly two advantages over the old approach:
    - once the kernel is created, the kernel gets immutable,
      which reduces some of the complexity which was caused due to a mutable kernel
    - having blueprints of the kernel and a factory to build everything
      enables us to build the modules and middlewares without running the kernel
      which makes it easier to build the the same kernel with different configurations

apiserver: added download handler (justtrackio#897)

This release adds a new type of API handler to the apiserver package: The `DownloadHandler` will act like a stream handler but don't require passing a JSON body. The goal is to provide a possibility for the server to answer a clients GET request (i.e. from a HTML anchor) with a streamed response (i.e. a file).

cloud: regenerate lambda api mocks;

cloud: regenerate lambda api mocks;

kernel/stage: kernels will now stop if a module returns an error; (ju…

…sttrackio#888)