Rename generateHeader to generateAuthorizationHeader for clarity

[melvincarvalho]

This issue is to address the function naming in the codebase to improve readability and understanding.

Please rename the function generateHeader to generateAuthorizationHeader. The new name better reflects the function's purpose, which is to generate an Authorization header for requests.

Code changes:

1. Update the function declaration:

   • Before: async function generateHeader(pubkey) { ... }
   • After: async function generateAuthorizationHeader(pubkey) { ... }

2. Update the function call in the save method:

   • Before: var authorization = await generateHeader(userHex)
   • After: var authorization = await generateAuthorizationHeader(userHex)