fix: sequelize field shadowing in models

[tmigone]

This fixes an issue where model public fields shadow sequelize setters/getters making models's actual data undefined.

indexer-agent  | (sequelize) Warning: Model "IndexingRule" is declaring public class fields for attribute(s): "id", "identifier", "identifierType", "allocationAmount", "allocationLifetime", "autoRenewal", "parallelAllocations", "maxAllocationPercentage", "minSignal", "minStake", "maxSignal", "minAverageQueryFees", "custom", "decisionBasis", "requireSupported", "safety", "protocolNetwork", "createdAt", "updatedAt".
indexer-agent  | These class fields are shadowing Sequelize's attribute getters & setters.
indexer-agent  | See https://sequelize.org/main/manual/model-basics.html#caveat-with-public-class-fields

For details see https://sequelize.org/docs/v6/core-concepts/model-basics/#caveat-with-public-class-fields