Adjust the default GraphQL complexity for queries that can potentially use indexation

[rafal-ch]

Basically, this issue is about resolving the following TODO in the code.

pub const DEFAULT_QUERY_COSTS: Costs = Costs {
    // TODO: The cost of the `balance` and `balances` query should depend on the
    //  `OffChainDatabase::balances_enabled` value. If additional indexation is enabled,
    //  the cost should be cheaper.
    balance_query: 40001,
    coins_to_spend: 40001,

If the "balances" or "coins to spend" indexation is available in the particular instance of the client, these costs should be lower.

Please note that the default cost is no longer "const", as it depends on the flag in offchain DB metadata (indexation_availability flag).

[anubhavitis]

@rafal-ch
I am interested to work on this issue. Can you help me with it please.

Based on what I understand, OffChainDatabase::balances_enabled value should determine the default cost of balance_query. But how do we calculate that in first place?

[rafal-ch]

Hi @anubhavitis
Thanks for offering to lend a hand but we're going to have to put a pin in this for now and think a bit about the best way forward.