Reana-server

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- Changes workflow scheduler to count number of workflow retries.

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- Adds Kubernetes job memory limits validation before publishing workflow submission.

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- Adds email validation to the ``user-create`` command used by the REANA administrators.
- Adds workflow name validation to the ``create_workflow`` endpoint.
- Changes ``/api/info`` endpoint to return a list of supported compute backends.
- Changes ``/api/status`` endpoint to calculate the cluster health status based on the availablity instead of the usage.

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- Changes ``quota-set`` command used by the REANA administrators to use the resource type along with a resource name for specifying the resource.
- Changes email validation used in ``create-admin-user`` command by the REANA administrators to be more permissive.

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- Adds users quota accounting.
- Adds support for Snakemake workflow engine.
- Adds ``include_progress`` and ``include_workspace_size`` query args to workflow list endpoint.
- Adds workflow prioritization in the queue by complexity.
- Adds ``priority`` and ``min_job_memory`` params to workflow submission publisher.
- Adds Yadage workflow specification loading to ``start_workflow`` endpoint.
- Adds a check in scheduler if at least one workflow job could be started in Kubernetes.
- Adds configuration environment variable to set workflow scheduling policy (``REANA_WORKFLOW_SCHEDULING_POLICY``).
- Adds configuration environment variable to set a timeout between consuming workflows (``REANA_SCHEDULER_REQUEUE_SLEEP``).
- Adds configuration environment variable to set an API rate limiter (``REANA_RATELIMIT_AUTHENTICATED_USER``, ``REANA_RATELIMIT_GUEST_USER``).
- Adds new ``info`` endpoint allowing to retrieve information about cluster capabilities such as available workspaces.
- Changes workflow execution consumer to receive only one message at a time.
- Changes to PostgreSQL 12.8

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- Changes internal dependencies.