Fix long description validation

[joshsmith]

Problem

EDIT: See the comment below.

We want to have a place for a Project to be explicitly approved by an admin.

[begedin]

This is pretty much done, in that the update action now supports setting approved: true on projects, and this change is only allowed by the policy if the user performing it is an admin.

The one thing we need to deal with, and this is a difficulty I've encountered while working on code-corps/code-corps-ember#1576

def changeset(struct, params) do
  struct
  |> cast(params, [:approval_requested, :cloudinary_public_id, :default_color, :description, :long_description_markdown, :title, :website])
  |> prefix_url(:website)
  |> validate_format(:website, CodeCorps.Helpers.URL.valid_format())
  |> validate_required([:title])
  |> generate_slug(:title, :slug)
  |> validate_slug(:slug)
  |> unique_constraint(:slug, name: :index_projects_on_slug)
  # this throws a validation error on update
  |> check_constraint(:long_description_markdown,
                      message: "cannot be deleted once your project is approved",
                      name: "set_long_description_markdown_if_approved")
  |> MarkdownRendererService.render_markdown_to_html(:long_description_markdown, :long_description_body)
end

The constraint is defined as

create constraint(
  :projects, 
  "set_long_description_markdown_if_approved", 
  check: "long_description_markdown IS NOT NULL OR approved = false")

What happens is

• during project creation, we do not validate long description as required
• during project approval, approved is set to true, but the project has no long description, so on update, validation fails

We need to either

• add validation to project creation
• remove the constraint
• add a way to notify the user as to why we can't approve

Adding a custom clause or subclause to Projects.update won't work, because the constraint is at db level, so will trigger in all cases.