feat: return the whole cache from GET /layer/{layerName}/{cacheType} MAPCO-11508

[razbroc]

Question	Answer
Bug fix	✔
New feature	✔
Breaking change	✖
Deprecations	✖
Documentation	✔
Tests added	✔
Chore	✖

Further information:

GET /layer/{layerName}/{cacheType} returned only the cache source — the inner cache section of a mapproxy cache. It now returns the whole cache as written in the configuration, alongside its name.

"Cache" means two things in a mapproxy config: the entry under caches: (sources, grids, format, upscale_tiles, …) and its inner cache: key that names the storage backend. This endpoint only ever exposed the second one.

{
  "cacheName": "example-layer",
  "cache": { "type": "s3", "directory": "…", "directory_layout": "tms" },
  "sources": [], "grids": ["epsg4326dir"], "format": "image/png", "upscale_tiles": 18
}

Not a breaking change

The cache source stays at the same cache key, so existing consumers read response.cache.* unchanged — the new fields are purely additive siblings. The only thing that would break is a consumer rejecting unknown response properties; none is known to.

The cache is spread verbatim, so mapproxy options we do not model (meta_size, cache_dir, …) are returned too. The response contract is deliberately "whatever the configuration holds" rather than our model of it — additionalProperties is left open and only cacheName + cache are required.

cacheType keeps its existing dual role unchanged: it selects the cache (-redis suffix) and validates it (400 when the resolved cache is of a different type).

Also in this PR

• caches was mistyped (separate commit). IMapProxyJsonDocument.caches was declared as a single IMapProxyCache instead of a map of them, so every caches[name] lookup resolved to any through the index signature and the casts around them were unchecked. Now Record<string, IMapProxyCache>, which typed four test lookups that had been silently any.
• ICacheObject/ICacheName → IGetCacheResponse. The request handler declared ICacheName as its response type while the manager returned ICacheObject — the response type was wrong. ICacheName had no other users.
• Guard for malformed cache entries. A caches entry that is not an object, or an object with no cache source, reached .cache.type and produced a 500 — and under verbatim spread would have produced corrupt output. It now raises the existing NotFoundError.
• Missing gpkgCache response schema. geopackage is an accepted cacheType, but getCacheResponse.cache had no geopackage variant and no discriminator mapping for it, so a real geopackage cache would have failed schema validation. Added with mapproxy's own option set and defaults (filename, table_name, levels, directory — all optional, type alone required).
• Fixed a test that asserted NotFoundError where the code throws BadRequestError; it passed only because Jest's toThrow(errorInstance) compares the message, not the class.

Verification

tsc clean · 47 unit + 19 integration tests passing · eslint 0 problems · redocly lint valid. The typing-fix commit was checked to build, lint, and pass tests standalone before the feature commit went on top.