json schema: improve provision activity date fields

* Improves title and description of dates in provision activity.
* Closes #1424.

Co-Authored-by: Alicia Zangger <alicia.zangger@rero.ch>

rero_ils/modules/documents/jsonschemas/documents/document_provision_activity-v0.0.1.json

@@ -209,8 +209,8 @@
           }
         },
         "startDate": {
-          "title": "Start date of publication",
-          "description": "Start date of the publication. This must be an integer, ie 1989, 453, -50. Used to sort search results. Once this field is set, a free formed date of publication can be added in the next field.",
+          "title": "Date 1",
+          "description": "Normalised date used for sorting and filtering options (MARC 008). A free text date (transcripted) can be added in the field \"Statements\".",
           "type": "integer",
           "minimum": -9999,
           "maximum": 2050,
@@ -224,8 +224,8 @@
           }
         },
         "endDate": {
-          "title": "End date of publication",
-          "description": "End date of the publication. This must be an integer, ie 1989, 453, -50. Used to sort search results. Once this field is set, a free formed date of publication can be added in the next field.",
+          "title": "Date 2",
+          "description": "Normalised end date if the provision activity covers more than one year, and used for sorting and filtering options (MARC 008). A free text date (transcripted) can be added in the field \"Statements\"",
           "type": "integer",
           "minimum": -9999,
           "maximum": 2050,