Register moves spaces to outbids while unconfirmed

[Ximik]

One can reproduce it with regtest

cargo run --bin space-cli -- --chain regtest open @creta

# mint blocks

cargo run --bin space-cli -- --chain regtest --output-format json listspaces
# {
#   "winning": [
#     {
#       "txid": "c4fa217b3913b4c8eed911ee58dd25f036b88b61f430afcc6e38f675d4e465ae",
#       "n": 1,
#       "name": "@creta",
#       "covenant": {
#         "type": "bid",
#         "burn_increment": 1000,
#         "signature": "ceae486bf186718504b20ac003d1cc3c5aef519ffc8b6a46400253a8abede60422a60381571be729dc4c1f8b22c522e81bf558d31c1803ec155f1e98a6628649",
#         "total_burned": 1000,
#         "claim_height": 5185
#       },
#       "value": 662,
#       "script_pubkey": "5120b334bd277b77a28b183c3b3af6b4467e5ab24dd5dbc2386dd2a3bc0e648557b2"
#     }
#   ],
#   "outbid": [],
#   "owned": []
# }

cargo run --bin space-cli -- --chain regtest register @creta

cargo run --bin space-cli -- --chain regtest --output-format json listspaces
# {
#   "winning": [],
#   "outbid": [
#     {
#       "txid": "c4fa217b3913b4c8eed911ee58dd25f036b88b61f430afcc6e38f675d4e465ae",
#       "n": 1,
#       "name": "@creta",
#       "covenant": {
#         "type": "bid",
#         "burn_increment": 1000,
#         "signature": "ceae486bf186718504b20ac003d1cc3c5aef519ffc8b6a46400253a8abede60422a60381571be729dc4c1f8b22c522e81bf558d31c1803ec155f1e98a6628649",
#         "total_burned": 1000,
#         "claim_height": 5185
#       },
#       "value": 662,
#       "script_pubkey": "5120b334bd277b77a28b183c3b3af6b4467e5ab24dd5dbc2386dd2a3bc0e648557b2"
#     }
#   ],
#   "owned": []
# }

It is related to #72. But in this case, it is unclear what would be the "correct" behaviour.

[Ximik]

Probably the nicest solution would be to have a separate "unconfirmed" or "pending" spaces group.
This would fix this issue and also prevent users from trying to "double spend".