Finish building Postgres support (#133)

This includes:
 - Building a Docker image for Postgres as well as SQLite
 - Fuller instructions for usage of the package, including the Postgres builds.

A few related things changed here:
 - `.env` is not used anymore -- the defaults in the Dockerfiles are
   sufficient
 - The Rust version in the Dockerfiles is increased to match the MSRV,
   and with it the Alpine version bumped to one built with that Rust
   version.
 - Cargo dependencies on native-tls and openssl updated to include only
   the `vendored` feature, so as not to require a system openssl
   installation.
 - Two GitHub jobs are set up, to build the two different Docker images
 - The documentation incorrectly suggested using `DELETE .. CASCADE` to
   delete clients. This syntax does not exist, as the cascading delete
   is configured in the schema.

docs/src/usage.md

@@ -1,87 +1,22 @@
 # Usage
 
-## Running the Server
+This repository is flexible and can be used in a number of ways, to suit your
+needs.
 
-The server is a simple binary that serves HTTP requests on a TCP port. The
-server does not implement TLS; for public deployments, the recommendation is to
-use a reverse proxy such as Nginx, haproxy, or Apache httpd.
+- If you only need a place to sync your tasks, using cloud storage may be
+cheaper and easier than running taskchampion-sync-server. See
+[task-sync(5)](http://taskwarrior.org/docs/man/task-sync.5/) for details on
+cloud storage.
 
-### Using Docker-Compose
+- If you have a publicly accessible server, such as a VPS, you can use `docker
+compose` to run taskchampion-sync-server as pre-built docker images. See
+[Docker Compose](./usage/docker-compose.md).
 
-Every release of the server generates a Docker image in
-`ghcr.io/gothenburgbitfactory/taskchampion-sync-server`. The tags include
-`latest` for the latest release, and both minor and patch versions, e.g., `0.5`
-and `0.5.1`.
+- If you would like more control, such as to deploy taskchampion-sync-server
+within an orchestration environment such as Kubernetes, you can deploy the
+docker images directly. See [Docker Images](./usage/docker-images.md).
 
-The
-[`docker-compose.yml`](https://raw.githubusercontent.com/GothenburgBitFactory/taskchampion-sync-server/refs/tags/v0.6.1/docker-compose.yml)
-file in this repository is sufficient to run taskchampion-sync-server,
-including setting up TLS certificates using Lets Encrypt, thanks to
-[Caddy](https://caddyserver.com/).
-
-You will need a server with ports 80 and 443 open to the Internet and with a
-fixed, publicly-resolvable hostname. These ports must be available both to your
-Taskwarrior clients and to the Lets Encrypt servers.
-
-On that server, download `docker-compose.yml` from the link above (it is pinned
-to the latest release) into the current directory. Then run
-
-```sh
-TASKCHAMPION_SYNC_SERVER_HOSTNAME=taskwarrior.example.com \
-TASKCHAMPION_SYNC_SERVER_CLIENT_ID=your-client-id \
-docker compose up
-```
-
-The `TASKCHAMPION_SYNC_SERVER_CLIENT_ID` limits the server to the given client
-ID; omit it to allow all client IDs.
-
-It can take a few minutes to obtain the certificate; the caddy container will
-log a message "certificate obtained successfully" when this is complete, or
-error messages if the process fails. Once this process is complete, configure
-your `.taskrc`'s to point to the server:
-
-```none
-sync.server.url=https://taskwarrior.example.com
-sync.server.client_id=your-client-id
-sync.encryption_secret=your-encryption-secret
-```
-
-The docker-compose images store data in a docker volume named
-`taskchampion-sync-server_data`. This volume contains all of the task data, as
-well as the TLS certificate information. It will persist over restarts, in a
-typical Docker installation. The docker containers will start automatically on
-system startup. See the docker-compose documentation for more information.
-
-### Running the Binary
-
-The server is configured with command-line options. See
-`taskchampion-sync-server --help` for full details.
-
-The `--listen` option specifies the interface and port the server listens on.
-It must contain an IP-Address or a DNS name and a port number. This option is
-mandatory, but can be repeated to specify multiple interfaces or ports. This
-value can be specified in environment variable `LISTEN`, as a comma-separated
-list of values.
-
-The `--data-dir` option specifies where the server should store its data. This
-value can be specified in the environment variable `DATA_DIR`.
-
-By default, the server will allow all clients and create them in the database
-on first contact. There are two ways to limit the clients the server will
-interact with:
-
-- To limit the accepted client IDs, specify them in the environment variable
-`CLIENT_ID`, as a comma-separated list of UUIDs. Client IDs can be specified
-with `--allow-client-id`, but this should not be used on shared systems, as
-command line arguments are visible to all users on the system. This convenient
-option is suitable for personal and small-scale deployments.
-
-- To disable the automatic creation of clients, use the `--no-create-clients`
-flag or the `CREATE_CLIENTS=false` environment variable. You are now
-responsible for creating clients in the database manually, so this option is
-more suitable for large scale deployments.
-
-The server only logs errors by default. To add additional logging output, set
-environment variable `RUST_LOG` to `info` to get a log message for every
-request, or to `debug` to get more verbose debugging output.
+- For even more control, or to avoid the overhead of container images, you can
+build and run the taskchampion-sync-server binary directly. See
+[Binaries](./usage/binaries.md).