Handle API errors when the token has issues (invalid or low credits)

[GaetanJuvin]

Re: issue #29

Expose @log_errors as a parameter and make it configurable.

client = Anthropic::Client.new(
  access_token: "access_token_goes_here",
  anthropic_version: "2023-01-01", # Optional
  request_timeout: 240 # Optional
  log_errors = true # Optional
)

Anthropic.configure do |config|
  config.access_token = ENV.fetch("ANTHROPIC_API_KEY")
  config.anthropic_version = "2023-01-01" # Optional
  config.request_timeout = 240 # Optional
  config.log_errors = true # Optional
end

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