Show is the documentation about how to use the header when it comes to authentication.
This is the documentation
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To use the functions described below, you need to make HTTP / HTTPS calls using the relevant method.
To ensure secure access, all requests require an authentication token which can be obtained by initializing a session. The token must be passed in the header of the HTTP call, specifically within the Authentication key.
To ensure greater performance to calls, it is recommended to use API Keys instead of Username / Password authentication. To use this mechanism you need to generate the API keys from the DocEasy interface (API Key and API Secret) then send them in each call inserted in the HTTP call header as follows (the values are all required):
APIKey - the value of the generated APIKey key
APISecret: The generated APISecret key value
Customer Code: the VAT number of the customer for whom you want to operate (provided you have the authorization)