OpenStreatMapのRelationからBoundaryを取得する

https://nominatim.openstreetmap.org/details?osmtype=[N|W|R]&osmid=<value>&class=<value>

https://nominatim.openstreetmap.org/details?osmtype=R&osmid=1761742&format=json&polygon_geojson=1

$ curl "https://nominatim.openstreetmap.org/details?osmtype=R&osmid=1761742&format=json&polygon_geojson=1"
{"place_id":377733871,"parent_place_id":225058060,"osm_type":"R","osm_id":1761742,"category":"boundary","type":"administrative","admin_level":7,"localname":"千代田区","names":{"name": "千代田区", "name:en": "Chiyoda", "name:es": "Chiyoda", "name:it": "Chiyoda", "name:ja": "千代田区", "name:ko": "치요다", "name:ru": "Тиёда", "name:zh": "千代田區", "name:ja-Hira": "ちよだく", "name:ja-Latn": "Chiyoda-ku", "name:zh-Hans": "千代田区", "name:zh-Hant": "千代田區", "name:eu": "Chiyoda", "_place_name:ko": "지요다구", "name:lt": "Čijoda", "name:pl": "Chiyoda", "name:th": "เขตชิโยดะ", "name:uk": "Чійода"},"addresstags":{"city": "東京都"},"country_code":"jp","indexed_date":"2024-02-05T06:29:39.574311+00:00","importance":0.5587954165289415,"calculated_importance":0.5587954165289415,"extratags":{"place": "city", "wikidata": "Q214051", "land_area": "administrative", "wikipedia": "ja:千代田区", "population": "46397", "linked_place": "city"},"calculated_wikipedia":"ja:千代田区","rank_address":18,"rank_search":14,"isarea":true,"centroid":{"type": "Point","coordinates": [139.7532163, 35.6938097]},"geometry":{"type":"Polygon","coordinates":[[[139.7301347,35.6850171],[139.73036,35.6842285],[139.7306814,35.6835905],[139.7315753,35.6818161],[139.7317655,35.6814442],[139.7319908,35.6813135],[139.7321081,35.6811725],[139.7324283,35.6807877],[139.7327555,35.6804348],[139.7330506,35.6798727],[139.7332276,35.6793149],[139.7336728,35.6789837],[139.7345526,35.6787833],[139.7349657,35.678731],[139.7354699,35.6787397],[139.7361995,35.6787833],[139.7362549,35.6787873],[139.7365642,35.6788094],[139.7366908,35.6784515],[139.7367091,35.6783998],[139.7367527,35.6782974],[139.7370845,35.6775179],[139.7371893,35.6771542],[139.7372599,35.676958],[139.737302,35.6768526],[139.7373269,35.6767908],[139.7373518,35.676738],[139.7373927,35.6766601],[139.7374737,35.6765335],[139.7376121,35.676366],[139.7378179,35.6761211],[139.7379009,35.676031],[139.7380445,35.6758492],[139.7382454,35.6754832],[139.7385667,35.6746946],[139.738612,35.6745832],[139.7386597,35.6744691],[139.7388623,35.6739841],[139.7389558,35.6738278],[139.7390724,35.6736859],[139.7391178,35.6736304],[139.7392009,35.6735436],[139.739622,35.6734059],[139.7414054,35.6722868],[139.7415453,35.6722835],[139.7416615,35.6722807],[139.7426326,35.6716532],[139.7430611,35.6714153],[139.7430782,35.6714058],[139.7431375,35.6713729],[139.7432612,35.6713343],[139.7433302,35.6713028],[139.7448604,35.6710108],[139.7450298,35.6710063],[139.7450303,35.6709556],[139.7450047,35.6707758],[139.7449233,35.670484],[139.745529,35.6703601],[139.7458145,35.6703101],[139.7467469,35.6702049],[139.7476254,35.669611],[139.7481371,35.6700215],[139.7485428,35.6703452],[139.7486929,35.6704575],[139.7494764,35.6709329],[139.7496691,35.6708749],[139.749778,35.6708377],[139.7516443,35.6701986],[139.7517363,35.6701671],[139.751791,35.670136],[139.75205,35.6706072],[139.7521006,35.670625],[139.7521975,35.6706011],[139.7527084,35.670475],[139.7534943,35.6702438],[139.7539141,35.6701048],[139.7552481,35.6696365],[139.7553525,35.6696124],[139.7554563,35.6695573],[139.7555403,35.6695209],[139.7556352,35.6694912],[139.7569026,35.6690942],[139.7569775,35.6690707],[139.7570626,35.6690442],[139.757918,35.6687804],[139.7580261,35.668747],[139.758555,35.6686296],[139.7585894,35.6687497],[139.7587553,35.6691331],[139.7587954,35.6691493],[139.7590301,35.6695726],[139.7593304,35.6701014],[139.7594914,35.6704106],[139.7595544,35.6705317],[139.7601156,35.6715201],[139.760398,35.6720175],[139.7604246,35.6720681],[139.7605227,35.6721907],[139.760642,35.6723283],[139.7607989,35.6724438],[139.7609881,35.6725382],[139.7611866,35.6726058],[139.7615956,35.672706],[139.7623183,35.6728919],[139.7625945,35.6729503],[139.7630775,35.6730622],[139.7636341,35.6732322],[139.7638888,35.6733513],[139.7639845,35.6734227],[139.7640914,35.6735024],[139.7641987,35.673632],[139.7644454,35.674021],[139.7646723,35.6744155],[139.764723,35.6745036],[139.7650679,35.674873],[139.765384,35.6752242],[139.7660313,35.6759278],[139.7661032,35.676006],[139.7668594,35.6770826],[139.7669439,35.6770506],[139.7670967,35.677018],[139.76722,35.6771998],[139.7673368,35.677372],[139.7670007,35.6774366],[139.767422,35.6781072],[139.7678664,35.6788156],[139.7683366,35.6795019],[139.768556,35.6798572],[139.7688243,35.6802947],[139.7689181,35.6804451],[139.769004,35.6805829],[139.7692744,35.6810051],[139.7694548,35.6813018],[139.7695423,35.6814333],[139.7696162,35.681534],[139.7695905,35.6815477],[139.7697253,35.6817137],[139.7697898,35.6817914],[139.7702577,35.6825007],[139.7703382,35.6826707],[139.770703,35.6834107],[139.7707124,35.6834278],[139.7707083,35.6834651],[139.7706989,35.6835007],[139.7706869,35.6835239],[139.7706466,35.6835653],[139.7706118,35.683577],[139.7706529,35.6836897],[139.77069,35.6837938],[139.7708089,35.6837658],[139.7708478,35.68376],[139.7708813,35.6837654],[139.7709108,35.6837774],[139.7709377,35.6838047],[139.7711603,35.6843366],[139.7708934,35.684394],[139.7709768,35.6846493],[139.7710472,35.6848649],[139.7708266,35.6852419],[139.7707916,35.6853221],[139.7704431,35.6861201],[139.7703882,35.6862458],[139.7700522,35.6866915],[139.769635,35.6871302],[139.7687983,35.6880099],[139.7679367,35.6885931],[139.768818,35.688873],[139.7690747,35.6889545],[139.7697075,35.6891658],[139.770351,35.6893787],[139.7710217,35.6895941],[139.77108,35.6896151],[139.7711112,35.6896228],[139.7722657,35.6899937],[139.7723383,35.690017],[139.7723895,35.690038],[139.7724413,35.6900593],[139.7725122,35.6900828],[139.7737709,35.6904989],[139.7738131,35.6905129],[139.7738654,35.6905302],[139.7748069,35.690842],[139.7748782,35.6908656],[139.7749502,35.6908895],[139.7752056,35.6909742],[139.775289,35.6910039],[139.776611,35.691459],[139.7775234,35.691851],[139.77876,35.6923346],[139.7797821,35.6930844],[139.7799412,35.6931966],[139.7800706,35.693085],[139.7802409,35.6928966],[139.7802878,35.6928379],[139.7804334,35.6929487],[139.7811087,35.693462],[139.7811911,35.6935246],[139.7812645,35.6935776],[139.7821969,35.6942517],[139.7827612,35.6946624],[139.7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