Require a custom user agent to use the SDK

[teolemon]

What

• Require a custom user agent to use the SDK
• Using the SDK and the API in general will remain as of today: free and accessible for everyone.
  IN the same way, we don't want to implement an API key mechanism and all that kind of stuff.
• However, due to misuse of the API through various SDKs, we will now force all language clients to have a valid User Agent so that we can reach out in case of problems.
• For now, We will only require an app name for the user agent.

[alexnguyen98]

@teolemon Is user agent required then? I am quite confused about the usage if the documentation states that it should be there but the library has no support for it. Thx

[bengeois]

@teolemon do you want a default user-agent for the SDK like "OpenFoodFacts - NodeJS", or do you want to force someone that use this SDK to provide a user-agent ?