Enhancement: cmip6 dataset-errata integration

[paolap]

Errata will be managed programatically in CMIP6 using ES-DOC

https://es-doc.org/cmip6-dataset-errata/

This is an extract on how it will be possible to search for errata:

"Search & View
Groups can search & view published errata via a simple to use web application which support two types of search:
Faceted: one can search by various facets such as institute, model, experiment, variable, severity & status.
PID: one can enter persistent identifers, i.e. PIDs. Each PID is resolved to the list of affected datasets and by extension the related errata."

So we should be able to use the PID from the files to check if any errata info exists and retrieve it.

[paolap]

I've been looking into this, unfortunately there seems to be such discrepancy in the way this is used, I doubt for the moment the all service is adding much information.
In a way I would focus first on returning the pids or tracking_ids.
We could see how complicated is then to integrate the "esdoc-errata-client" to use its' errata search functionality, the errata url contained in the es-doc always redirect to the mail errata page not to a potential record for that simulation.
I suppose Csiro would need this to publish their model output

[paolap]

Created esdoc.py with errata and esdoc functions, we can now retrieve and print errata from tracking_id and esdoc for CMIP6 based on dataset_ids.
For CMIP5 only idcc from CERA service is available, this also has some information on models for CMIP6.
Haven't checked a cortex example yet but I assume that should work in the same way at least for CMIP6 cortex, need to check if anything at all available for older cordex.
New functions are in notebook including text, still missing the link to cli.py. Link to this is issue #37

[paolap]

The functions and tests for them are now in master, there still no way to call them from the command line

[paolap]

Possible options for command line

Adding flag --docs followed by a document type, this should trigger the creation of a doc file with the information.

Adding flag --verbose extra option to be used with docs to have shorter or longer version of documents
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