How to store API authentication password?

I am connecting a WP site to a service through the service API.

The API authentication of this service is done using the service account username and password, not API keys:

• You send a request to the service API and give the account username and password.
• You receive a token, valid for a number of hours, that allows you to make API requests.

The problem that I see is that the service account password will have to be stored in the WP database, to be used in the API authentication.

I can encrypt the password in the database, but in a way that allows it to be decrypted back to a simple text form, which is not secure.

I cannot encrypt it into a hash, store the hash and use that for the authentication.

What is the best practice for storing the password in this situation?