docs: added guidebook entry for Lookup To GitLab Sync

Closes uis/devops/devhub/lookup-gitlab-sync/faas#10 (closed)

docs/services/lookup-gitlab-sync.md

+# Lookup To GitLab Sync
+
+This page gives an overview of the Lookup To GitLab Sync service, describing its current status, where
+and how it's developed and deployed, and who is responsible for maintaining it.
+
+## Service Description
+
+The Lookup To GitLab Sync service blocks and unblocks users in the GitLab University
+Developers' Hub.
+
+University users present in Lookup will be blocked in GitLab if they are cancelled in Lookup.
+By the same token, they will be unblocked in GitLab if they were previously blocked by this
+service, but are now no longer cancelled in Lookup.
+
+Also, external users who's accounts have been inactive for 24 months will by blocked in GitLab.
+
+## Service Status
+
+The Lookup To GitLab Sync service is currently beta.
+
+## Contact
+
+Technical queries and support should be directed to [cloud@uis.cam.ac.uk](mailto:cloud@uis.cam.ac.uk)
+and will be picked up by a member of the team working on the service. To ensure that you receive a
+response, always direct requests to [cloud@uis.cam.ac.uk](mailto:cloud@uis.cam.ac.uk) rather than
+reaching out to team members directly.
+
+Issues discovered in the service or new feature requests should be opened as
+`[GitLab issues in the application repository](https://gitlab.developers.cam.ac.uk/uis/devops/devhub/lookup-gitlab-sync/faas)`.
+
+## Environments
+
+The `Lookup To GitLab Sync` is currently deployed to the following environments:
+
+| Name        | Cloud Scheduler | URL                |
+| ----------- | --------------- | ------------------ |
+| Production  | [lookup-gitlab-sync-0](https://console.cloud.google.com/cloudscheduler?project=lgsync-prod-fcc24789) | [lookup-gitlab-sync](https://lookup-gitlab-sync-685393389588.europe-west2.run.app) |
+| Staging     | [lookup-gitlab-sync-0](https://console.cloud.google.com/cloudscheduler?project=lgsync-test-b2c4b48b)| [lookup-gitlab-sync](https://lookup-gitlab-sync-272453387498.europe-west2.run.app) |
+| Development | [lookup-gitlab-sync-0](https://console.cloud.google.com/cloudscheduler?project=lgsync-devel-1492c1e2) | [lookup-gitlab-sync](https://lookup-gitlab-sync-685393389588.europe-west2.run.app) |
+
+## Source code
+
+The source code for the Lookup To GitLab Sync is spread over the following repositories:
+
+| Repository  | Description |
+| ----------- | ------------------ |
+| [Application Server](https://gitlab.developers.cam.ac.uk/uis/devops/devhub/lookup-gitlab-sync/faas) | The source code for the main application server |
+| [Infrastructure Deployment](https://gitlab.developers.cam.ac.uk/uis/devops/devhub/lookup-gitlab-sync/infrastructure) | The Terraform infrastructure code for deploying the application server to GCP |
+
+## Technologies used
+
+The following gives an overview of the technologies the Lookup To GitLab Sync service is built on.
+
+| Category | Language | Framework(s) |
+| -------- | -------- | --------- |
+| Server | Python 3.11 | [ucam-faas](https://gitlab.developers.cam.ac.uk/uis/devops/lib/ucam-faas-python) |
+| GCP deployment  | Terraform  1.7 | Google Cloud Platform |
+
+## Operational documentation
+
+The following gives an overview of how the Lookup To GitLab Sync is deployed and maintained.
+
+### How and where the Lookup to Gitlab Sync service is deployed
+
+Deployment is via our standard [terraform deployment CI
+pipeline](https://gitlab.developers.cam.ac.uk/uis/devops/continuous-delivery/ci-templates/-/blob/master/auto-devops/terraform-pipeline.yml?ref_type=heads).
+
+### Deploying a new release
+
+Making a new release of the application is done via [release
+automation](../explanations/gitlab-release-automation.md). In short: merged commits are collected
+together into a draft "next release" Merge Request. When merged, a new release tag is pushed to the
+repository along with a Docker image being pushed to Google's Artefact registry.
+
+Deployment is done by:
+
+1. Updating the deployment project's repository with any changes, including bumping the deployed web
+   application release.
+2. Using the "play" buttons in the CI pipeline to deploy to production when happy. (Deployments to
+   **staging** happen automatically on merges to `main`.)
+
+### Monitoring
+
+Monitoring is configured as per our standard Google Cloud Run application module.
+
+## Service Management and tech lead
+
+The **service owner** for the Lookup to Gitlab Sync service is [Abraham Martin](https://www.lookup.cam.ac.uk/person/crsid/amc203).
+
+The **service manager** for the Lookup to Gitlab Sync service is [Adam Deacon](https://www.lookup.cam.ac.uk/person/crsid/ad2139).
+
+The **tech lead** for the Lookup to Gitlab Sync service is [Roy Harrington](https://www.lookup.cam.ac.uk/person/crsid/rh841).
+
+The following engineers have operational experience with the Lookup To GitLab Sync service and are
+able to respond to support requests or incidents:
+
+- [Roy Harrington](https://www.lookup.cam.ac.uk/person/crsid/rh841)
+- [Stephen Ison](https://www.lookup.cam.ac.uk/person/crsid/si202)
+- [Ryan Kowalewski](https://www.lookup.cam.ac.uk/person/crsid/rk725)
+- [Dmitrii Unterov](https://www.lookup.cam.ac.uk/person/crsid/du228)
+- [Sam Wenham](https://www.lookup.cam.ac.uk/person/crsid/sdw37)