[#21] locode: Introduce locode overriding

Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>

pkg/locode/table/csv/table.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"io/fs"
 	"sync"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-locode-db/pkg/locode"
 )
 
 // Prm groups the required parameters of the Table's constructor.
@@ -21,6 +23,11 @@ type Prm struct {
 	//
 	// Must not be empty.
 	SubDivPath string
+
+	// Path to a csv table with UN/LOCODE overrides.
+	//
+	// Optional.
+	OverridesPath string
 }
 
 // Table is a descriptor of the UN/LOCODE table in csv format.
@@ -39,6 +46,8 @@ type Table struct {
 	subDivOnce sync.Once
 
 	mSubDiv map[subDivKey]subDivRecord
+
+	overrides map[locode.LOCODE]locode.Record
 }
 
 const invalidPrmValFmt = "invalid parameter %s (%T):%v"
@@ -67,9 +76,15 @@ func New(prm Prm, opts ...Option) *Table {
 		opts[i](o)
 	}
 
-	return &Table{
+	t := &Table{
 		paths:      append(o.extraPaths, prm.Path),
 		mode:       o.mode,
 		subDivPath: prm.SubDivPath,
 	}
+
+	if err := t.initOverrides(prm.OverridesPath); err != nil {
+		panic(fmt.Errorf("init overrides: %w", err))
+	}
+
+	return t
 }