10217 source name harvesting client

[luddaniel]

What this PR does / why we need it:

This PR will help admin to customize their harvesting clients name in metadata source facet.
A new field called sourceName, a nullable TEXT, has been added.
If set, it will overload the nickName in metadata source facet while indexing harvested dataset.
This will allow to have many harvesting client to be under the same sourceName if wished.

Please have in mind that displaying nickName or sourceName requires to activate the feature flag index-harvested-metadata-source.

This PR contains some refactoring and update on guide documentation.

Which issue(s) this PR closes:

• Closes Add Source/Server name to OAI-PMH Harvesting clients #10217

Special notes for your reviewer:

I tested this code from user interface (Dashboard > create and edit havesting client popup) .
I tested this code from API also.
I was not able to test the HarvestingClientsIT in localhost.

My samples for testing :

{
"nickName": "CIRAD_1",
"dataverseAlias": "root",
"type": "oai",
"style": "dataverse",
"harvestUrl": "https://dataverse.cirad.fr/oai",
"archiveUrl": "https://dataverse.cirad.fr",
"archiveDescription": "This Dataset is harvested from our partners. Clicking the link will take you directly to the archival source of the data.",
"metadataFormat": "oai_dc",
"set": "entrepot_recherche_data_gouv",
"schedule": "none",
"allowHarvestingMissingCVV": false,
"useOaiIdentifiersAsPids": false
}

{
"nickName": "IRD",
"sourceName": "RDG Partners",
"dataverseAlias": "root",
"type": "oai",
"style": "dataverse",
"harvestUrl": "https://dataverse.ird.fr//oai",
"archiveUrl": "https://dataverse.ird.fr",
"archiveDescription": "This Dataset is harvested from our partners. Clicking the link will take you directly to the archival source of the data.",
"metadataFormat": "oai_dc",
"schedule": "none",
"allowHarvestingMissingCVV": false,
"useOaiIdentifiersAsPids": false
}

{
"nickName": "progedo",
"sourceName": "RDG Partners",
"dataverseAlias": "root",
"type": "oai",
"style": "default",
"harvestUrl": "https://data.progedo.fr/oai",
"archiveUrl": "https://data.progedo.fr",
"archiveDescription": "This Dataset is harvested from our partners. Clicking the link will take you directly to the archival source of the data.",
"metadataFormat": "oai_dc",
"schedule": "none",
"allowHarvestingMissingCVV": true,
"useOaiIdentifiersAsPids": false
}

Does this PR introduce a user interface change?:

The new field is visible in both creation and edition harvesting client popup :

Examples of harvesting result in metadata source :

Please note that both progedo and IRD are merged under "RDG Partners" in metadata source and CIRAD is displayed under CIRAD because the sourceName is not set.

Is there a release notes update needed for this change?

Yes

[coveralls]

coverage: 22.751% (-0.001%) from 22.752%
when pulling 668ac77 on Recherche-Data-Gouv:10217-source-name-harvesting-client
into aebec05 on IQSS:develop.