Improve error message for top-level schema-validation errors

[maddenp-noaa]

Synopsis

Given a.jsonschema

{
  "additionalProperties": false,
  "properties": {
    "n": {
      "type": "integer"
    }
  },
  "required": [
    "n"
  ],
  "type": "object"
}

and a.yaml

x: 42

Old behavior:

$ uw config validate --schema-file a.jsonschema --input-file a.yaml 
[2024-12-19T04:30:37]    ERROR 2 schema-validation errors found in config
[2024-12-19T04:30:37]    ERROR Error at :
[2024-12-19T04:30:37]    ERROR   Additional properties are not allowed ('x' was unexpected)
[2024-12-19T04:30:37]    ERROR Error at :
[2024-12-19T04:30:37]    ERROR   'n' is a required property

Note that Error at : is not useful, and looks like something is missing.

New behavior:

$ uw config validate --schema-file a.jsonschema --input-file a.yaml 
[2024-12-19T04:30:43]    ERROR 2 schema-validation errors found in config
[2024-12-19T04:30:43]    ERROR Error at top level:
[2024-12-19T04:30:43]    ERROR   Additional properties are not allowed ('x' was unexpected)
[2024-12-19T04:30:43]    ERROR Error at top level:
[2024-12-19T04:30:43]    ERROR   'n' is a required property

I think we haven't run into this yet because the driver configs we've been evaluating don't have useful content at the top level; instead, we immediately look under a key (e.g. ungrib:) for a specific driver and validate that. Once again, using uwtools in new contexts points out areas for improvement.

Type

• Bug fix (corrects a known issue)

Impact

• This is a non-breaking change (existing functionality continues to work as expected)

Checklist

• I have added myself and any co-authors to the PR's Assignees list.
• I have reviewed the documentation and have made any updates necessitated by this change.