fix: config to support keys with special values (#9304)

This PR adds context-based `k=v` splits based
on the sub-system which was obtained, if the
keys are not provided an error will be thrown
during parsing, if keys are provided with wrong
values an error will be thrown. Keys can now
have values which are of a much more complex
form such as `k="v=v"` or `k=" v = v"`
and other variations.

additionally, deprecate unnecessary postgres/mysql
configuration styles, support only

- connection_string for Postgres
- dsn_string for MySQL

All other parameters are removed.

cmd/config/config_test.go

@@ -17,7 +17,94 @@
 
 package config
 
-import "testing"
+import (
+	"testing"
+)
+
+func TestKVFields(t *testing.T) {
+	tests := []struct {
+		input          string
+		keys           []string
+		expectedFields map[string]struct{}
+	}{
+		// No keys present
+		{
+			input:          "",
+			keys:           []string{"comment"},
+			expectedFields: map[string]struct{}{},
+		},
+		// No keys requested for tokenizing
+		{
+			input:          `comment="Hi this is my comment ="`,
+			keys:           []string{},
+			expectedFields: map[string]struct{}{},
+		},
+		// Single key requested and present
+		{
+			input:          `comment="Hi this is my comment ="`,
+			keys:           []string{"comment"},
+			expectedFields: map[string]struct{}{`comment="Hi this is my comment ="`: {}},
+		},
+		// Keys and input order of k=v is same.
+		{
+			input: `connection_string="host=localhost port=2832" comment="really long comment"`,
+			keys:  []string{"connection_string", "comment"},
+			expectedFields: map[string]struct{}{
+				`connection_string="host=localhost port=2832"`: {},
+				`comment="really long comment"`:                {},
+			},
+		},
+		// Keys with spaces in between
+		{
+			input: `enable=on format=namespace connection_string=" host=localhost port=5432 dbname = cesnietor sslmode=disable" table=holicrayoli`,
+			keys:  []string{"enable", "connection_string", "comment", "format", "table"},
+			expectedFields: map[string]struct{}{
+				`enable=on`:        {},
+				`format=namespace`: {},
+				`connection_string=" host=localhost port=5432 dbname = cesnietor sslmode=disable"`: {},
+				`table=holicrayoli`: {},
+			},
+		},
+		// One of the keys is not present and order of input has changed.
+		{
+			input: `comment="really long comment" connection_string="host=localhost port=2832"`,
+			keys:  []string{"connection_string", "comment", "format"},
+			expectedFields: map[string]struct{}{
+				`connection_string="host=localhost port=2832"`: {},
+				`comment="really long comment"`:                {},
+			},
+		},
+		// Incorrect delimiter, expected fields should be empty.
+		{
+			input:          `comment:"really long comment" connection_string:"host=localhost port=2832"`,
+			keys:           []string{"connection_string", "comment"},
+			expectedFields: map[string]struct{}{},
+		},
+		// Incorrect type of input v/s required keys.
+		{
+			input:          `comme="really long comment" connection_str="host=localhost port=2832"`,
+			keys:           []string{"connection_string", "comment"},
+			expectedFields: map[string]struct{}{},
+		},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run("", func(t *testing.T) {
+			gotFields := kvFields(test.input, test.keys)
+			if len(gotFields) != len(test.expectedFields) {
+				t.Errorf("Expected keys %d, found %d", len(test.expectedFields), len(gotFields))
+			}
+			found := true
+			for _, field := range gotFields {
+				_, ok := test.expectedFields[field]
+				found = found && ok
+			}
+			if !found {
+				t.Errorf("Expected %s, got %s", test.expectedFields, gotFields)
+			}
+		})
+	}
+}
 
 func TestValidRegion(t *testing.T) {
 	tests := []struct {