Better console messages when API key is invalid

[hhkaos]

Describe the problem

I just realized that when using an invalid API key the error message is not intuitive at all:

Describe the proposed solution

I would prefer a console error by showing Invalid API key or access token or something like that.

Alternatives considered

No response

Additional Information

I noticed I'm not the first one struggling with this xD

[gavinr]

Thanks for the suggestion. Seems like a good idea to me.

[sdthaker]

Since I'm quite new to this repository, wanted to know what would be the best way to test the code changes made for this issue. Would that be to open the HTML files in the example directory (after running npm run build) and check to see if the API calls are managed properly in the console and whether the proper log is shown to the user? Thanks! @gavinr-maps

[sdthaker]

Also, the tests are failing for spec/VectorTileLayerSpec.js after making the changes in src/VectorTileLayer.js to throw an error when api key or token is not provided. However, the tests are passing for spec/VectorBasemapLayerSpec.js because each test case passes either an api key or token when testing different cases. Does that mean that test cases for spec/VectorTileLayerSpec.js need to be updated so now each test case passes an api key or token at the very least? Please let me know if this makes sense. Thanks! @gavinr-maps