[rbardaji]

Closes #374.

What

Every installer run is appended to install.log in the checkout (--log-file <path> to choose, /dev/null to turn it off):

• a header per run: UTC time, git describe of the installer, the arguments (values of --ckan-password, --ckan-api-key, --s3-access-key, --s3-secret-key masked), user and host, Federation URL;
• everything the run printed, stdout and stderr, without colour codes;
• appended, never truncated, mode 600;
• a failure ends with install log: <path>;
• a log that cannot be written is reported and the run carries on.

The terminal output is unchanged on both streams.

Tests

• New install/tests/test_install_log.py (11 tests; 10 fail on main).
• Real test: a real install of an Endpoint on a laptop with Docker (build, start, health check) produced the log with header and full output, no colour codes; a failing run ended with the log path on screen and in the file.

Release 0.34.59.