Support custom mapId in GeoJsonFolder config

[MisterGC]

Problem

Currently, the GeoJsonFolder data source derives the mapId automatically from the folder path using mapNameFromUri(). This transformation:

1. Converts to lowercase
2. Replaces :, \, /, . with dashes
3. Collapses consecutive dashes
4. Removes -openapi-json suffix

For example, /home/user/geodata becomes -home-user-geodata.

Users cannot override this behavior to set a meaningful, custom mapId.

Proposed Solution

Add an optional mapId property to the GeoJsonFolder configuration schema. If provided, use it directly; otherwise, fall back to the current mapNameFromUri() derivation.

Example config:

dataSources:
  - type: GeoJsonFolder
    folder: /path/to/my/geodata
    mapId: my-custom-map  # optional
    withAttrLayers: true

Implementation

The GeoJsonSource constructor already supports an optional mapId parameter - it just needs to be wired through the config layer.