Add help text to wfjt launch endpoint.

awx/api/templates/api/workflow_job_template_launch.md

@@ -0,0 +1,29 @@
+Launch a Workflow Job Template:
+
+Make a GET request to this resource to determine if the workflow_job_template
+can be launched and whether any passwords are required to launch the
+workflow_job_template. The response will include the following fields:
+
+* `can_start_without_user_input`: Flag indicating if the workflow_job_template
+  can be launched without user-input (boolean, read-only)
+* `variables_needed_to_start`: Required variable names required to launch the
+  workflow_job_template (array, read-only)
+* `survey_enabled`: Flag indicating whether the workflow_job_template has an
+  enabled survey (boolean, read-only)
+* `extra_vars`: Text which is the `extra_vars` field of this workflow_job_template
+  (text, read-only)
+* `warnings`: JSON object listing warnings of all workflow_job_template_nodes
+  contained in this workflow_job_template (JSON object, read-only)
+* `workflow_job_template_data`: JSON object listing general information of
+  this workflow_job_template (JSON object, read-only)
+
+Make a POST request to this resource to launch the workflow_job_template. If any
+passwords, inventory, or extra variables (extra_vars) are required, they must
+be passed via POST data, with extra_vars given as a YAML or JSON string and
+escaped parentheses.
+
+If successful, the response status code will be 201.  If any required passwords
+are not provided, a 400 status code will be returned.  If the workflow job cannot
+be launched, a 405 status code will be returned. If the provided credential or
+inventory are not allowed to be used by the user, then a 403 status code will
+be returned.