[HOTFIX] Move AZURE_SCOPE to config to allow chaning it for IMAP or GRAPH modes

AZURE_SCOPE is different is IMAP or GRAPH modes. Move it to config, with Graph mode by default.

    # for IMAP_AUTHENTICATION_MODE=xoauth2
    # AZURE_SCOPE = [
    #     "https://outlook.office.com/IMAP.AccessAsUser.All",
    # ]

    # for IMAP_AUTHENTICATION_MODE=xoauth2graph
    AZURE_SCOPE = [
        "https://graph.microsoft.com/.default",
    ]