088 project template defaults: Flow PT REST finding

Q Can a script read which task template a project uses for each entity type?

Endpoint GET /schema/Project/fields ; POST /entity/projects/_search ; POST /entity/project_task_template_connections/_search ; GET /preferences

Docs claim Silent. tracking_settings is typed serializable with no declared structure (field_types/serializable).

Actual

Project fields naming a template or a setting
  task_templates     multi_entity ['TaskTemplate'] editable
  tracking_settings  serializable                  editable
  is_template, is_template_project  checkbox, read only (the project flags, not task templates)

22 projects; tracking_settings key paths, projects holding each
  navchains.Asset 21   navchains.Cut 22   navchains.CutItem 22   navchains.Shot 20   navchains.Sequence 1
  default_task_template present on 6, non-empty on 1
  Shot: true on 1
project A: {"default_task_template": {"Asset": {"type": "TaskTemplate", "id": 40,
            "name": "<template>", "valid": "valid"}}}
  GET /entity/task_templates/40 -> 200; in project A's task_templates: False
five projects: {"default_task_template": {}}

Project.task_templates non-empty on 1 of 22: [{"id": 46, "name": "<template>", "type": "TaskTemplate"}]
ProjectTaskTemplateConnection: fields project, task_template, cached_display_name; 1 row, the same pair
TaskTemplate.projects: the same 1 pair; the three agree
GET /preferences: 17 keys, none naming a template or a task

Teaches

where	holds	readable
`Project.tracking_settings.default_task_template.<EntityType>`	the default template for that type, as `{type, id, name, valid}`	yes, `?fields=tracking_settings`
`Project.task_templates`	a list of templates attached to the project	yes
`ProjectTaskTemplateConnection`	the join row behind `task_templates`	yes, `/entity/project_task_template_connections`
`TaskTemplate.projects`	the same list from the other side	yes
`/preferences`	nothing about templates	n/a

The default and the attached list are different data. On the probed site the one project with a default for Asset does not list that template in task_templates. Read the default from tracking_settings, never infer it from the list.
On the probed site default_task_template is absent on 16 projects and {} on 5. Absent, {} and a missing entity-type key all mean no default. valid read "valid"; no other value was seen.
tracking_settings is a blob: no filter reaches into it (field_types/serializable), so finding projects with a default means reading every project's value.
Whether the API applies the default is unmeasured. Probe 083 found task_template: null on a create generates nothing in a project with no default. Send task_template explicitly rather than rely on the project default.