Version-control poetry.lock with Git

tiangolo#69
tiangolo#123
tiangolo#144
tiangolo/full-stack-fastapi-template@00297f9

Commit 00297f9 gitignored poetry.lock. This commit will add poetry.lock
to version control with Git to avoid dependency resolution errors during
Docker builds.

There is no established convention for working with Poetry in Docker,
so developers have to consider each use case individually. See:
python-poetry/poetry#1879 (comment)

In this project, the Dockerfile copies poetry.lock into the Docker image,
but there's no step to generate poetry.lock in the first place. Without
poetry.lock, dependency resolutions are commonly seen, such as:

```text
❯ bash scripts/test.sh

WARNING: The following deploy sub-keys are not supported and have been ignored: labels
WARNING: The following deploy sub-keys are not supported and have been ignored: labels
WARNING: The following deploy sub-keys are not supported and have been ignored: labels
WARNING: The following deploy sub-keys are not supported and have been ignored: labels
WARNING: The following deploy sub-keys are not supported and have been ignored: labels
db uses an image, skipping
flower uses an image, skipping
pgadmin uses an image, skipping
proxy uses an image, skipping
queue uses an image, skipping
Building backend
[+] Building 15.3s (8/10)
 => [internal] load build definition from backend.dockerfile                                      0.2s
 => => transferring dockerfile: 797B                                                              0.1s
 => [internal] load .dockerignore                                                                 0.1s
 => => transferring context: 2B                                                                   0.0s
 => [internal] load metadata for ghcr.io/br3ndonland/inboard:fastapi-python3.9                    0.3s
 => [1/6] FROM ghcr.io/br3ndonland/inboard:fastapi-python3.9@sha256:5591f436a37490a1569afd9e55ae  0.0s
 => [internal] load build context                                                                 0.0s
 => => transferring context: 64.67kB                                                              0.0s
 => CACHED [2/6] COPY ./app/pyproject.toml ./app/poetry.lock* /app/                               0.0s
 => CACHED [3/6] WORKDIR /app/                                                                    0.0s
 => ERROR [4/6] RUN bash -c "if [ true == 'true' ] ; then poetry install --no-root ; else poetr  14.4s
------
 > [4/6] RUN bash -c "if [ true == 'true' ] ; then poetry install --no-root ; else poetry install --no-root --no-dev ; fi":
 Skipping virtualenv creation, as specified in config file.
 Installing dependencies from lock file
 Warning: The lock file is not up to date with the latest changes in pyproject.toml. You may be getting   dependencies. Run update to update them.

   SolverProblemError

   Because app depends on sqlalchemy-stubs (^0.3) which doesn't match any versions, version solving failed.

   at /opt/poetry/lib/poetry/puzzle/solver.py:241 in _solve
       237│             packages = result.packages
       238│         except OverrideNeeded as e:
       239│             return self.solve_in_compatibility_mode(e.overrides, use_latest=use_latest)
       240│         except SolveFailure as e:
     → 241│             raise SolverProblemError(e)
       242│
       243│         results = dict(
       244│             depth_first_search(
       245│                 PackageNode(self._package, packages), aggregate_package_nodes
------
executor failed running [/bin/sh -c bash -c "if [ $INSTALL_DEV == 'true' ] ; then poetry install --no-root ; else poetry install --no-root --no-dev ; fi"]: exit code: 1
ERROR: Service 'backend' failed to build : Build failed
```

.gitignore

@@ -1,5 +1,5 @@
 .vscode
 testing-project
 .mypy_cache
-poetry.lock
+# poetry.lock
 dev-link/