function getCacheKey(source, tileCoord) {
  return `${getUid(source)},${source.getKey()},${source.getRevision()},${getTileCoordKey(tileCoord)}`;
}
@param {import("../../source/Tile.js").default} source The source.
@param {import('../../tilecoord.js').TileCoord} tileCoord The tile coordinate.
@return {string} The cache key.