Document DSN password URL-encoding requirement for MySQL connection string

[josecelano]

I'm working on a new repo to automate the tracker deployment (still experimental), and I have realised we can have problems with the DB passwords automatically generated.

When configuring the tracker with a MySQL DSN (e.g. mysql://user:password@host:3306/db), reserved URL characters in the password (notably + and /) must be percent-encoded. Otherwise, the DSN may be parsed incorrectly, and the tracker fails to connect to MySQL despite correct credentials.

In the official deployment tutorial, we use SQLite, so this is not a problem.

Why this matters

In many deployments, the DSN is built from environment variables (e.g. docker-compose). If MYSQL_PASSWORD contains reserved characters, the URL becomes invalid unless encoded first.

Standard secret generators produce base64 strings that include + and /, which are problematic in the URL password component.

Symptoms

• Tracker fails to start or cannot connect to MySQL
• Auth errors from MySQL despite the correct user password
• Errors trace back to the DSN parsing

Proposed improvements

1. Documentation: Add a short note in configuration docs clarifying that credentials in DSNs must be URL-encoded, with a quick example (e.g. Python urllib.parse.quote or shell snippet) and/or recommend URL-safe secrets (A–Z, a–z, 0–9, -, _).

2. Examples: Ensure docker-compose examples either:

• Use URL-safe secrets for MYSQL_PASSWORD, or
• Show how to provide an already-encoded value in the DSN

3. (Optional) Alternative config: Consider supporting separate config fields for user/password (not embedded in the DSN), to avoid URL-encoding pitfalls.

cc @da2ce7