Feature request: Implement stronger_soldier as a two-step server-tracked daily task

[tickBit]

What do you want to see in the API?

The task should progress when the reserved player:

1. Increases the attack value of their own defence soldier through PUT /customCharacter.
2. Plays a battle afterwards, detected from the existing battle win/loss daily task event flow.

The API should send normal daily task MQTT progress/completion notifications:

• Step 1 completed:
  /player/{playerId}/daily_task/stronger_soldier/update
• Task completed after battle:
  /player/{playerId}/daily_task/stronger_soldier/end
• Clan completion:
  /clan/{clanId}/daily_task/stronger_soldier/end
• Possible milestone:
  /clan/{clanId}/daily_task/milestone/update

How do you think this should work?

Current code already has the useful pieces:

• ServerTaskName.STRONGER_SOLDIER = 'stronger_soldier'
• GET /customCharacter returns the logged-in player’s custom characters.
• CustomCharacter.player_id identifies the owning player.
• CustomCharacter.attack is returned as the current total attack value.
• PUT /customCharacter updates character stats in CustomCharacterController.update.
• Battle completion already emits ServerTaskName.GO_TO_BATTLE from GameEventsHandler.handleWinBattle and handleLoseBattle.

Suggested backend flow:

flowchart TD
    A[Reserved task: stronger_soldier] --> B[PUT /customCharacter]
    B --> C[Read previous CustomCharacter stats]
    C --> D[Update CustomCharacter]
    D --> E{Is this player's own defence soldier<br/>and did attack increase?}
    E -->|No| F[No stronger_soldier progress]
    E -->|Yes| G[Progress stronger_soldier step 1<br/>amountLeft 2 -> 1]
    G --> H[MQTT TASK_UPDATED]

    H --> I[Player plays battle]
    I --> J[Battle win/loss event]
    J --> K{Reserved stronger_soldier<br/>with step 1 already done?}
    K -->|No| L[No stronger_soldier completion]
    K -->|Yes| M[Complete stronger_soldier<br/>amountLeft 1 -> 0]
    M --> N[Player/clan rewards]
    N --> O[MQTT TASK_COMPLETED + CLAN_TASK_COMPLETED]

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Implementation detail suggestion:

• In CustomCharacterController.update / CustomCharacterService, compare the character’s previous attack value to the new attack value before/after update.
• Only progress stronger_soldier if:
  • the logged-in player owns the character,
  • the active reserved daily task is stronger_soldier,
  • the updated character is a defence soldier,
  • attack increased.
• Set stronger_soldier.amount = 2, so step 1 leaves amountLeft = 1.
• Do not complete the task during the stat update.
• On battle win/loss handling, complete stronger_soldier only if it is the player’s active reserved task and amountLeft === 1.
• Preserve the existing GO_TO_BATTLE behavior for the normal go_to_battle task.

Any additional info?

Note that CustomCharacterService.addValues() adds base stats to stored stat deltas before returning characters. So attack comparison should be done carefully: either compare normalized total values or compare stored deltas consistently.