FujiOracle - setPriceFeed should check asset and priceFeed decimals
`getPriceOf()` assumes that all price feeds return prices with identical decimals, but `setPriceFeed` does not enforce this. Potential misconfigurations can have severe effects on the system's internal accounting.\\n```\\n/\\*\\*\\n \\* @dev Sets '\\_priceFeed' address for a '\\_asset'.\\n \\* Can only be called by the contract owner.\\n \\* Emits a {AssetPriceFeedChanged} event.\\n \\*/\\nfunction setPriceFeed(address \\_asset, address \\_priceFeed) public onlyOwner {\\n require(\\_priceFeed != address(0), Errors.VL\\_ZERO\\_ADDR);\\n usdPriceFeeds[\\_asset] = \\_priceFeed;\\n emit AssetPriceFeedChanged(\\_asset, \\_priceFeed);\\n}\\n```\\n
We recommend adding additional checks to detect unexpected changes in assets' properties. Safeguard price feeds by enforcing `priceFeed` == address(0) || priceFeed.decimals() == `8`. This allows the owner to disable a `priceFeed` (setting it to zero) and otherwise ensure that the feed is compatible and indeed returns `8` decimals.
```\\n/\\*\\*\\n \\* @dev Sets '\\_priceFeed' address for a '\\_asset'.\\n \\* Can only be called by the contract owner.\\n \\* Emits a {AssetPriceFeedChanged} event.\\n \\*/\\nfunction setPriceFeed(address \\_asset, address \\_priceFeed) public onlyOwner {\\n require(\\_priceFeed != address(0), Errors.VL\\_ZERO\\_ADDR);\\n usdPriceFeeds[\\_asset] = \\_priceFeed;\\n emit AssetPriceFeedChanged(\\_asset, \\_priceFeed);\\n}\\n```\\n