Release 1.0.0

Added
^^^^^

* Support for deleted records. (Implements `#3`_)

  * The deletedRecords value (in response to Identify-verb) is configurable via
    ``--oai-pmh-deleted-records`` and defaults to value `transient`.

* Configuration option to limit the list size of each metadataformat separately.
  (Implements `#2`_)
* New metadataformat OAI Datacite with prefix `oai_datacite`.
* Plugin architecture for developing arbitrary metadataformats & OAI-sets.
* Support insecure (unverified SSL certificate chain) https connections in list_records.py
  via configuration flag ``--insecure``. Default is to reject insecure connections.
* Generate setName values for ``language`` and ``data_kind`` sets which do not have one.
  (Implements `#24`_)
* Command line entrypoint `kuha_list_records` outputs deleted record count and
  supports HTTP Basic Authentication. (Implements `#25`_)

Changed
^^^^^^^

* Require Kuha Common 1.0.0.
* Plenty of API changes to facilitate the developing of metadataformats as plugins:

  * Delete configure.py. Serve-endpoint configuration is now declared in
    serve.py. Modules declare configurations via their respective add_cli_args
    functions.
  * Add controller.py. The controller is responsible for gathering
    the OAI responses from metadataformats.
  * Add http_api.py. This module declares the HTTP interface and dispatches
    requests to the configured controller. The module contains minimum
    amount of non-server imports and calls to controller.
  * Add metadataformats-package, which replaces the oai/metadata_formats.py
    and oai/records.py modules.
  * serve.py loads and configures metadataformats using entrypoint-group
    ``kuha.oai.metadataformats``. No metadataformats are directly imported.
  * oai/__init__.py now contains add_cli_args & configure methods to
    configure package classes. It defines a Protocol-class which
    wraps all OAI-PMH protocol objects.

* Update dependencies in requirements.txt.

  * Tornado 6.1.0
  * ConfigArgParse 1.5.3
  * six 1.16.0

Removed
^^^^^^^

* Drop support for Python versions below Python 3.8.

Fixed
^^^^^

* Repeat EAD3 daterange element when a record has multiple date
  ranges. (Fixes `#20`_)
* Metadata rendered by prefix `oai_ddi25` should place
  distrbtr-element before distDate-element in distStmt.
  (Fixes `#21`_)