Most of the applications today are using Azure KeyVault to store secrets.

Azure Key Vault is a cloud service for securely storing and accessing secrets. A secret is anything that you want to tightly control access to, such as API keys, passwords, certificates, or cryptographic keys.

Reference: What is Azure Key Vault?

How to configure your local machine

Safe storage of app secrets in development in ASP.NET Core

1. Open your Visual Studio > right-click in your project > select the option “Manage User Secrets”
   Note: I created this documentation with Visual Studio 2022

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   Note: the secrets are storage on C:\Users\<windowsuser>\AppData\Roaming\Microsoft\UserSecrets. To create a secret by command line, you can use
   
   

   dotnet user-secrets set "Movies:ServiceApiKey" "12345"

    

2. Add this structure and run your project

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   Note: If you have this error when you run the project, maybe the structure of the keys is not correct.

How to configure pipeline with Azure