Report PL_API_KEY usage in `planet auth value`

[cholmes]

When debugging an early user's CLI it took some digging before I realized that PL_API_KEY was set and being used, since it didn't show up in planet auth value. It'd be good to give the user some indication what key will actually be used, over the one reported in value. My suggested route would be for planet auth value to say something like 'API Key set in PL_API_KEY environment variable:` and show that API key instead of the one they logged in with. But open to other ways to solve this.

[cholmes]

Should also warn on planet auth init

[tschaub]

I hit this same issue and agree that the CLI messages could make it easier to figure out what is going on.

When running planet auth init or planet auth value, if PL_API_KEY is set, it would be helpful if the CLI could say that it will be preferred over the planet auth configured value.

For example, something like this would be helpful:

> planet auth value
XYZ-123
Warning: The PL_API_KEY environment variable is set to a different value than the one above.
The PL_API_KEY variable takes precedence and will be used instead of the above value in API requests.

If something like this is printed from planet auth value, it should go to STDERR so that the value from STDOUT can still be used (e.g. curl -u $(planet auth value): https://api.planet.com/compute/ops/orders/v2 should still work).

In addition, the message printed when planet orders list (or other requests) fails with a 401 could be more helpful. The API responds with "API key not found" in the case of a 401. Currently, the CLI prints out this same "API key not found" message. From the perspective of a CLI user, this sounds like the CLI could not find my API key for use with the API.

For example, a message like this would be less confusing:

> planet orders list
Unable to list orders with the provided credentials.

Since the CLI knows what auth mechanism is being used, the message could even be more specific (e.g. "Unable to list orders with the API key in the PL_API_KEY environment variable.")

[sgillies]

I think I found some low hanging fruit. At https://github.com/planetlabs/planet-client-python/blob/main/planet/cli/auth.py#L59 (planet auth value) we could get the active auth object (which is not necessarily from a file, planet.auth by design supports more sources than that) that we have stored in ctx and report based on its properties. That's a good start. To complement this we could add a source property to the APIKeyAuth class https://github.com/planetlabs/planet-client-python/blob/main/planet/auth.py#L198. With the new property, planet auth value could print something like 0123456789abcdef0123456789abcdef (from /home/me/.planet.json).

It's also worth warning about discrepancy between keys in the secret file and environment 👍

[jreiberkyle]

Per #808, the CLI will only always use secret file for configuration. Therefore, this ticket (reporting PL_API_KEY usage in CLI) is no longer needed. The CLI will provide a helpful warning if PL_API_KEY is set when planet auth login or planet auth init are run.