cc_phone_home.py would benefit from allowing headers for the request to be specified by the user

This bug was originally filed in Launchpad as [LP: #1771174](https://bugs.launchpad.net/cloud-init/+bug/1771174)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2018-05-14T18:00:44.254686+00:00

date_fix_committed = None

date_fix_released = None

id = 1771174

importance = wishlist

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1771174

milestone = None

owner = dpneumo

owner_name = Mitch Kuppinger

private = False

status = triaged

submitter = dpneumo

submitter_name = Mitch Kuppinger

tags = []

duplicates = []

_Launchpad user **Mitch Kuppinger(dpneumo)** wrote on 2018-05-14T18:00:44.254686+00:00_

I user phone_home to programmatically set allowed_hosts on my management node when creating cloud based VMs. eg. on DigitalOcean. I use a Rails based tool to manage the VM creation. Without some workarounds that lower security I receive a "Can't verify CSRF token authenticity." error from Rails when phone_home attempts to connect. The ability to set a header would be very useful:

phone_home:
    url: http://example.com/$INSTANCE_ID/
    post:
        - pub_key_rsa
        - instance_id
        - fqdn
    tries: 10
    headers: { X-CSRF-Token: 1234567890 } #<<<<<<<

Since util.read_file_or_url allows specifying headers
minor modifications to cc_phone_home.py would make this possible:

line 85:
    url = ph_cfg['url']
    post_list = ph_cfg.get('post', 'all')
    header_dict = ph_cfg.get('headers', {}) #<<<<< Added
    tries = ph_cfg.get('tries')

line 138:
    try:
      util.read_file_or_url(url, data=real_submit_keys,
                            retries=tries, sec_between=3,
                            ssl_details=util.fetch_ssl_details(cloud.paths),
                            headers=header_dict) #<<<<< Added