oauth login impl

[xavluiz]

• [x] implement oauth0 support
• [x] swap localStorage with auth provider session

AuthProvider.ts --> fetch sessions public async getSessions(scopes?: string[]): Promise<readonly AuthenticationSession[]>

"A storage utility for secrets. Secrets are persisted across reloads and are independent of the current opened workspace.

const allSessions = await this.context.secrets.get(SESSIONS_KEY);"