Upgrade project deps

upgrade.md

Useful commands:

• composer outdated (check for outdated packages);
• composer why-not (check for version constraints not allowing us to upgrade);
• composer recipes:update - update symfony-packages automatically;

In order to upgrade symfony to a new version, consider following 3-step the scenario:

Step 1:

Upgrade all dev packages to the latest versions, so that CI would be able to run on new set of dev-packages.

Step 2:

1. Upgrade all outdated third-party packages, except symfony/* (though, it would be nice to upgarde symfony to latest minor version).
2. Run & fix tests
3. Commit, deploy

Step 3: when it has all been successfully tested and works correctly, perform the main upgarde:

1. Upgarde symfony packages (remember, currently there should be not that much dependency issues, because of first phase).
2. Run & fix tests;
3. Upgrade rest of the packages to the newest version
4. Run & fix tests;
5. Commit, deploy