feat: ensure consistent handling of "not found" errors

[Junjiequan]

Description

This PR aims to correct inconsistent and wrong error handling messages.

e.g, The following code returns Unauthorized, even if the true reason is the proposal is not found.

  private async checkPermissionsForProposal(
    request: Request,
    id: string,
    group: Action,
  ) {
    const proposal = await this.proposalsService.findOne({
      proposalId: id,
    });

    const canDoAction = this.permissionChecker(group, proposal, request);

    if (!canDoAction) {
      throw new ForbiddenException("Unauthorized to this proposal");
    }
    return proposal;
  }

Motivation

Wrong error handling increases debug difficulties and misleading

Fixes

• Bug fixed (#X)

Changes:

• changes made

Tests included

• Included for each change/fix?
• Passing?

Documentation

• swagger documentation updated (required for API changes)
• official documentation updated

official documentation info