Tweak documentation

docs/developer_guide.md

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+# Developer's guide
+
+This guide assume you have some knoweldge of [ActivityPub](https://activitypub.rocks/).
+
+[TOC]
+
+## Architecture
+
+Microblog.pub is a "modern" Python application with "old-school" server-rendered templates.
+
+ - [Poetry](https://python-poetry.org/) is used for dependency management.
+ - Most of the code is asynchronous, using [asyncio](https://docs.python.org/3/library/asyncio.html).
+ - SQLite3 is the default database.
+
+The server has 2 components:
+
+ - The web server (powered by [FastAPI](https://fastapi.tiangolo.com/) and [Jinja2](https://jinja.palletsprojects.com/en/3.1.x/) templates)
+ - An additional process that takes care of sending "outgoing actities" 
+
+## Tasks
+
+The project uses [Invoke](https://www.pyinvoke.org/) to manage tasks (a Python powered Makefile).
+
+You can find the tasks definition in `tasks.py` and list the tasks using:
+
+```bash
+inv -l
+```
+
+### Media storage
+
+The uploads are stored in the `data/` directory, using a simple content-addressed storage (file contents hash is the name of the store BLOB).
+Files metadata are stored in the database.
+
+## Installation
+
+Running a local version requires:
+
+ - Python 3.10+
+ - SQLite 3.35+
+
+You can follow the [Python developer version of the install instructions](https://docs.microblog.pub/installing.html#python-developer-edition).
+
+## Documentation
+
+The documention is managed as Markdown files in `docs/` and the online documentation is built using a homegrown Python script (`scripts/build_docs.py`).
+
+You can build the documentation locally by running:
+
+```bash
+inv build-docs
+```
+
+And check out the result by starting a static server using Python standard library:
+
+```bash
+cd docs/dist
+python -m http.server 8001
+```