painter: decode semi-colon from monitoring history

The plugin output and comments are saved in a Nagios-compatible format
(semi-colon-separated). Therefore, it is necessary to escape semi-colons
to `%3B` when writing out history.

In the GUI, where plugin output or comments from the monitoring history
are displayed, we can translate `%3B` back to a semi-colon using a
simple replace.

Although this is not 100% correct (`%3B` could have been in the original
text), it will probably do the right thing in 99.9% of use cases and is
therefore a valid fix for now.

SUP-20926

Change-Id: Id45bc9da05907582b2e398044d387bac3618775b

cmk/gui/painter/v0/painters.py

@@ -8,6 +8,7 @@
 from collections.abc import Callable, Iterable, Mapping, Sequence
 from fnmatch import fnmatch
 from pathlib import Path
+from typing import Literal
 
 import cmk.utils.man_pages as man_pages
 import cmk.utils.paths
@@ -4459,12 +4460,12 @@ def columns(self) -> Sequence[ColumnName]:
         return ["log_plugin_output", "log_type", "log_state_type", "log_comment"]
 
     def render(self, row: Row, cell: Cell) -> CellSpec:
-        output = row["log_plugin_output"]
-        comment = row["log_comment"]
-        if output:
+        if output := self._decode_item(row, column="log_plugin_output"):
             return "", format_plugin_output(output, row)
-        if comment:
+
+        if comment := self._decode_item(row, column="log_comment"):
             return "", comment
+
         log_type = row["log_type"]
         lst = row["log_state_type"]
         if "FLAPPING" in log_type:
@@ -4476,6 +4477,12 @@ def render(self, row: Row, cell: Cell) -> CellSpec:
             return "", (lst + " - " + log_type)
         return "", ""
 
+    @staticmethod
+    def _decode_item(row: Row, *, column: Literal["log_plugin_output", "log_comment"]) -> str:
+        """Decode escaped characters coming from Nagios history monitoring."""
+        # TODO: decode all escaped characters coming from monitoring history.
+        return row.get(column, "").replace("%3B", ";")
+
 
 class PainterLogWhat(Painter):
     @property