Container file resource

[jtopjian]

This commit adds the lxd_container_file resource which can be used
to manage individual files in a container.

This depends on #112

I can rebase afterwards or all 3 commits can be merged here.

Can also add docs once #114 is added.

[mjrider]

I'm wondering why you want to move the file subresource to a seperate resource
from the following 2 examples, i think the second is the most readable, and has the least surprises, so which scenario are you trying to cover here?

resource "lxd_container" "container1" {
   name = "foobar"
   image = "images:alpine/3.5"
   profiles = ["default"]
 }
 
 resource "lxd_container_file" "file1" {
   container_name = "${lxd_container.container1.name}"
   remote  = "${lxd_container.container1.remote}"
   target_file = "/foo/bar.txt"
   content = "Hello, World!\n"
   create_directories = true
 }

vs

resource "lxd_container" "container1" {
   name = "foobar"
   image = "images:alpine/3.5/amd64"
   profiles = ["default"]
   file {
     target_file = "/foo/bar.txt"
     content = "Hello, World!\n"
     create_directories = true
   }
 }

[jtopjian]

@mjrider See my comments in #112

Additionally, when a resource has "sub-resources" that tend to have a one-to-many relationship, they always work better as separate resources in the long term. For example, by having a separate file resource, the file can be treated as a first-class resource and have dedicated count and depends_on arguments.

[sl1pm4t]

What would be the problem you see with keeping the original embedded file sub resource along side the standalone resource?
I know it would some caveats ( the two resources compete and TF will see a diff on each run ) but it seems to be a commonly accepted pattern in other providers. e.g google_container_cluster that includes a node_pool sub resource vs the standalone google_container_node_pool resource.

[jtopjian]

Rebased and docs added.

[mjrider]

@jtopjian what do you think about sl1pm4t suggestion for keeping the subresource version , so users can have a choice in what they need/want

[jtopjian]

@mjrider That was my intention all along 😄

[shantanugadgil]

FWIW, I don't mind having only a separate resource.

[sl1pm4t]

LGTM with one tiny typo found.

[sl1pm4t]

typo - santize -> sanitize

[sl1pm4t]

That was my intention all along 😄

Sorry for the confusion, when I read through the PR comments on my phone I somehow got the impression you were removing the embedded resource. Might be because there was another PR for deprecated a resource, and I confused the two.

Anyway it looks good to me.

[jtopjian]

No problem at all!

I detailed my plans for this in #112. I should have added those notes here as well, so it's my fault for the confusion.

Thank you for catching the typo.