Implement richer, fully customizable logging; customizable timestamps (#1)

- `@kanta.logemit` handler for completely customizable logging output, with `LogEvent` structure and `kanta.tty.Line` helper to create colorized text and fixed width fields
- `configure_logging(diff=False)` to disable diff display globally (supplementing per-transaction `logdiff=False`)
- `transaction(extra: Any = ...)` for passing extra strings or custom metadata to logs
- `@kanta.clock` to provide user controlled clock for deterministic database outputs
- Added a demo script that shows basic functions, migrations, logfmt etc.

tests/test_logging.py

@@ -2,16 +2,39 @@ import logging
 
 import pytest
 
-from kanta.logging import configure_logging, log_change, transaction_logger
+from kanta.logging import (
+    configure_logging,
+    format_action_header,
+    log_change,
+)
+from kanta.tty import ESC
+
+
+def test_format_action_header():
+    header = format_action_header("update", "alice", "tgt")
+    assert header == (
+        f"{ESC}1;34mupdate{ESC}0m {ESC}38;5;250mtgt{ESC}0m by {ESC}34malice{ESC}0m"
+    )
+
+
+def test_format_action_header_action_only():
+    assert format_action_header("update") == f"{ESC}1;34mupdate{ESC}0m"
 
 
 @pytest.fixture(autouse=True)
 def _reset_kanta_loggers():
     yield
-    for name in ("kanta", "kanta.transaction", "kanta.bootstrap", "kanta.migration"):
+    for name in (
+        "kanta",
+        "kanta.transaction",
+        "kanta.transaction.diff",
+        "kanta.bootstrap",
+        "kanta.migration",
+    ):
         logger = logging.getLogger(name)
         logger.setLevel(logging.NOTSET)
         logger.propagate = True
+        logger.disabled = False
         logger.handlers.clear()
 
 
@@ -46,3 +69,48 @@ def test_log_change_no_diff(capsys):
     log_change("test", {})
     captured = capsys.readouterr()
     assert "test" in captured.err
+
+
+def test_log_change_appends_extra_string(capsys):
+    kanta_logger = logging.getLogger("kanta")
+    kanta_logger.handlers.clear()
+    configure_logging()
+    log_change("export", {}, extra="mydb.db")
+    captured = capsys.readouterr()
+    assert "export" in captured.err
+    assert f"{ESC}38;5;250mmydb.db{ESC}0m" in captured.err
+
+
+def test_log_change_log_diff_false(capsys, monkeypatch):
+    kanta_logger = logging.getLogger("kanta")
+    kanta_logger.handlers.clear()
+    configure_logging()
+
+    def _boom(*args, **kwargs):
+        raise AssertionError("format_diff should not be called")
+
+    monkeypatch.setattr("kanta.logging.format_diff", _boom)
+    log_change("update", {"counter": 5}, previous={}, log_diff=False)
+    captured = capsys.readouterr()
+    assert "update" in captured.err
+    assert "counter" not in captured.err
+
+
+def test_configure_logging_diff_false(capsys):
+    kanta_logger = logging.getLogger("kanta")
+    kanta_logger.handlers.clear()
+    configure_logging(diff=False)
+    log_change("update", {"counter": 5}, previous={})
+    captured = capsys.readouterr()
+    assert "update" in captured.err
+    assert "counter" not in captured.err
+
+
+def test_configure_logging_diff_true_reenables(capsys):
+    kanta_logger = logging.getLogger("kanta")
+    kanta_logger.handlers.clear()
+    configure_logging(diff=False)
+    configure_logging(diff=True)
+    log_change("update", {"counter": 5}, previous={})
+    captured = capsys.readouterr()
+    assert "counter" in captured.err