Datacite

- Updates package setup and adds black formatting
- Adds support for DataCite Metadata Schema v4.5.
The version 4.5 jsonschema includes a number of
changes and improvements:

- Switches to jsonschema 2019-09 and adds more complete validation
to catch mistyped elements
- Switches publisher from a string to an object. This means
you will need to change publisher to be structured like
`"publisher": {"name": "Invenio Software"}`
when you use version 4.5. This change is needed to
support the addition of publisher identifiers.
- Removes the identifiers field and added doi, prefix, and suffix fields.
These fields are clearer, and DataCite appears to be moving away from the
combined identifiers field. doi is not a required field since you may or
may not have a DOI depending on your workflow.
- Adds new relatedItem elements for publication metadata
- Switches geolocation point values to numbers. This is to enable
validation and is consistent with GeoJson and InvenioRDM. It is
different from the DataCite REST API which uses strings, and
submitted numbers will be turned into strings by DataCite.
- Reorganizes geolocationPolygon to how DataCite is currently rendering this
metadata
- Adds support for the new resourceTypeGeneral and relationType values
- General jsonschema organization improvements

- Updates dependency versions and adds python 3.9 support
- Changes internal definition name for affiliation in 4.3 schema

- Standardizes function names in DataCiteRESTClient. Old functions will be
depreciated in a future release

- Fixes DataCiteRESTClient attributes' type. Prefix, username and password
are always cast to string.

- Adds full support for DataCite Metadata Schema v4.2 and v4.3 XML generation.
- Uses Official DataCite JSON Schema, which has the following notable changes
from the previous schema:

- Uses "identifiers" which is a combination of the XML "identifier" and
"alternativeIdentifiers" elements
- "creatorName" is now "name"
- "contributorName" is now "name"
- "affiliations" is now "affiliation" (is still an array)
- "affilition" is now "name"
- There is no longer a funder identifier object (the identifier and type are just
elements)
- Removes Python 2 support
- Removes the old way of testing with DataCite: test mode for the MDS APIs and
the test DOI 10.5072

- Fixes schema location url for DataCite v4.1