feat: updated dockerfile, deps, guide & fix src

- fix logical error, better non 200 resp message in main.py
- updated dependencies
- major updates to contributing guide
- quicker prod builds with reduced docker layers
- adds dockerfile for development
- updates github action for unit-tests

dockerfile

@@ -0,0 +1,26 @@
+FROM python:slim-bullseye
+
+ENV PYTHONFAULTHANDLER=1 \
+    PYTHONUNBUFFERED=1 \
+    PYTHONHASHSEED=random \
+    PYTHONDONTWRITEBYTECODE=1 \
+    # pip:
+    PIP_NO_CACHE_DIR=off \
+    PIP_DISABLE_PIP_VERSION_CHECK=on \
+    PIP_DEFAULT_TIMEOUT=100 \
+    # poetry:
+    # POETRY_VERSION=1.1.14 \
+    POETRY_NO_INTERACTION=1 \
+    POETRY_CACHE_DIR=/var/cache/pypoetry \
+    PATH=${PATH}:/root/.local/bin
+
+# copy project files
+COPY pyproject.toml poetry.lock main.py /
+
+# install poetry & dependencies
+RUN apt-get update && apt-get install --no-install-recommends -y curl \
+    && curl -sSL https://install.python-poetry.org | python - \
+    && poetry install --no-root --no-ansi --only main
+
+# copy and run program
+CMD [ "poetry", "run", "python", "/main.py" ]