feat: Add logic to export and import etcd catalog keys as JSON

[subkanthi]

…ON to catalog.

closes: ##27
closes: #176

[subkanthi]

Export

ice catalog-export -o catalog_export.json
2026-05-21 15:23:20 [49717579-57/47868] INFO c.a.i.r.c.i.r.CatalogAdminServlet > Exported 1 namespace(s) and 13 table(s)
2026-05-21 15:23:20 [main/74519] INFO com.altinity.ice.cli.Main > Wrote catalog snapshot to catalog_export.json

Delete all keys

etcdctl del --prefix ""

Import

ice catalog-import -i catalog_export.json          
2026-05-21 15:25:25 [49717579-38/47868] INFO c.a.i.r.c.i.r.CatalogAdminServlet > Import: 14 created, 0 skipped, 0 overwritten
{
  "created" : 14,
  "skipped" : 0,
  "overwritten" : 0,
  "catalog_name" : "default",
  "exported_at" : "2026-05-21T20:23:20.555925Z"
}

ice list-tables ontime            
2026-05-21 15:26:57 [49717579-41/47868] INFO c.a.i.r.c.i.r.RESTCatalogServlet > @token:anonymous GET v1/config
2026-05-21 15:26:57 [49717579-42/47868] INFO c.a.i.r.c.i.r.RESTCatalogServlet > @token:anonymous GET v1/namespaces/ontime/tables
---
namespace: ontime
tables:
- ontime.testmay6_17_01
- ontime.testmay6_19_01
- ontime.testmay7_13_01
- ontime.testmay7_15_01
- ontime.testmay7_16_01
- ontime.testmay7_16_02
- ontime.testmay7_17_02
- ontime.testmay7_17_03
- ontime.testmay7_17_04
- ontime.testmay7_17_05
- ontime.testmay7_17_06
- ontime.testmay7_17_07
- ontime.testmay9_17_07

[xieandrew]

Functionality looks good, tested locally with 1 and 3 node etcd using docker compose. I have a couple comments on a potential security issue with the endpoints and an edge case error.

Also, it would be nice if there was a test in EtcdCatalogIT for this, but we could add it in a later PR.

[xieandrew]

Looks good to me