Token invalid

[MatthewJWhittle]

Received this error when using get_token()

`Error in get_layer_details(endpoint = endpoint, my_token = my_token) :

• code: 498
• message: Invalid token.
• details: Invalid token.`

I suspect that it is due to the access_token expiring. Need to add some functionality to check for this and request a new access token.

The problem was fixed by deleting the cached token and running get_token.

[MatthewJWhittle]

This is now resolved in the development branch