Edit a Meta campaign

Changes a campaign's name, status or lifetime spend cap. The spend cap is a hard ceiling on everything the campaign will ever spend, expressed as a decimal in the account currency. Use when: renaming for clarity, or putting a hard ceiling on a campaign the user wants to bound. Do not use to pause or resume — meta_pause_entity and meta_resume_entity exist so the risk of the change is stated correctly to the user. Do not set a spend cap below what the campaign has already spent: Meta stops delivery immediately and the campaign cannot be revived by lowering it further. Returns the campaign read back from Meta. At least one of name, status or spend_cap must be given.