✨ Add support for nested fields in log entries and JSON marshalling

This commit introduces the ability to handle nested fields within log entries.
The  file has been updated with a  function
that transforms flat keys with a : delimiter (e.g., obj:foo) into nested
JSON objects (e.g., ).

The  file includes new test cases to verify that:
- Nested fields are correctly unmarshalled from string representations.
- Nested fields are correctly marshalled into JSON objects.

This enhancement allows for more structured and organized metadata within log entries.

models/entry_test.go

@@ -125,6 +125,14 @@ func TestEntryUnmarshal(t *testing.T) {
 			[]Meta{{"me", json.RawMessage(`{"name":"Dan","coder":true}`)}},
 			nil,
 		},
+		{
+			"nested-field",
+			"@begin " + whens + " - A Title\n@me:name Dan\n@me:coder true @end",
+			"A Title",
+			when,
+			[]Meta{{"me:name", "Dan"}, {"me:coder", true}},
+			nil,
+		},
 		{
 			"json-field",
 			"@begin " + whens + " - Some Guy\n" + `@json {"name":"Dan","coder":true} @end`,
@@ -209,6 +217,8 @@ func TestEntryJsonMarshal(t *testing.T) {
 		{"obj-field", "A Title", when, []Meta{{"obj", json.RawMessage(`{"foo":"bar","title":"Sub-title"}`)}}, `{"title":"A Title","date":"` + whens + `","obj":{"foo":"bar","title":"Sub-title"}}`, nil},
 		{"date-field", "A Title", when, []Meta{{"when", when.Add(time.Hour)}}, `{"title":"A Title","date":"` + whens + `","when":"` + when.Add(time.Hour).Format(time.RFC3339) + `"}`, nil},
 		{"json-field", "A Title", when, []Meta{{"json", json.RawMessage(`{"age": 41, "cool": true, "name": "Jim"}`)}}, `{"title":"A Title","date":"` + whens + `","age":41,"cool": true, "name": "Jim"}`, nil},
+		{"nested-field", "A Title", when, []Meta{{"obj:foo", "bar"}, {"obj:title", "Sub-title"}}, `{"title":"A Title","date":"` + whens + `","obj":{"foo":"bar","title":"Sub-title"}}`, nil},
+		{"double-nested-field", "A Title", when, []Meta{{"obj:foo", "bar"}, {"obj:me:name", "Dan"}, {"obj:me:age", 27}}, `{"title":"A Title","date":"` + whens + `","obj":{"foo":"bar","me":{"name":"Dan","age":27}}}`, nil},
 	}
 
 	for _, tt := range tests {