feat(#635): allow changing refresh request body via json pointer

[phoenix-ru]

🔗 Linked issue

Closes #635

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This allows setting custom refresh request body to allow usages with external backends

📝 Checklist

• I have linked an issue or discussion.
• I have added tests (if possible).
• I have updated the documentation accordingly.

[MisterNox]

I came across the same issue today. We should also do it for the signOut method as libraries like django simple jwt require to have the refresh token in the body for their standard blacklist class. This means rawRefreshToken.value = null should be moved after the fetch. And res = await _fetch(nuxt, path, { method, headers }) needs to be adjusted like you did in the refresh method to res = await _fetch(nuxt, path, { method, headers, body: objectFromJsonPointer(refreshRequestTokenPointer, refreshToken.value) }). What do you think?