How to generate the JWT token using Prisma API?

The service token is a simple JWT token that can easily be created by using service and stage name, as well as the secret. You can create the token yourself and attach it. Take a look at the actual code the prisma CLI is using:

  getToken(serviceName: string, stageName: string): string | undefined {
    if (this.secrets) {
      const data = {
        data: {
          service: `${serviceName}@${stageName}`,
          roles: ['admin'],
        },
      }
      return jwt.sign(data, this.secrets[0], {
        expiresIn: '7d',
      })
    }

    return undefined
  }

Source: https://github.com/prisma/prisma/blob/master/cli/packages/prisma-yml/src/PrismaDefinition.ts

More information regarding the structure:

Service tokens follow the JSON Web Token (JWT) specification (RFC 7519):

"JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted."

A JWT has the following three components:

Header: The header typically consists of two parts: the type of the token, which is JWT, and the hashing algorithm being used (which is HS256 in the case of Prisma service tokens).

{   "alg": "HS256",   "typ": "JWT" } 

Payload: The payload contains the claims. Claims are statements about an entity (typically, the user) and additional data. Here is what it looks like for a service called demo deployed to the dev stage:

{   
   "data": {
      "service": "demo@dev",
      "roles": ["admin"]   
   },   
   "iat": 1532530208,   
   "exp": 1533135008 
} 

Signature: The signature is used to verify the message wasn't changed along the way. To create the signature part you have to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that. For example if you want to use the HMAC SHA256 algorithm, the signature will be created in the following way:

HMACSHA256(base64UrlEncode(header) + '.' + base64UrlEncode(payload), secret) 

Therefore, a JWT typically looks like this: xxxxx.yyyyy.zzzzz

Source: https://www.prisma.io/docs/prisma-server/authentication-and-security-kke4/#service-token