api: add metadata + template api lifting

models/document.go

models/metadata.go

models/render_request.go

models/render_template_request.go

models/template.go

restapi/embedded_spec.go

restapi/operations/logging.go

restapi/operations/prometheus.go

restapi/operations/rednerd_api.go

restapi/operations/rendering/render_one_parameters.go

restapi/operations/rendering/render_one_urlbuilder.go

...operations/template_management/template_add_parameters.go

.../operations/template_management/template_add_responses.go

restapi/operations/template_management/template_update.go

...rations/template_management/template_update_parameters.go

...rations/template_management/template_update_prometheus.go

...erations/template_management/template_update_responses.go

...rations/template_management/template_update_urlbuilder.go

...tions/template_management/user_template_add_parameters.go

...ations/template_management/user_template_add_responses.go