Document disableoperations functionality

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Document disableoperations functionality
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QuickSightEmbedSession: a
.model({
id: a.string().required(),
userAlias: a.string().required(),
dashboardId: a.string().required(),
embedUrl: a.string().required(),
createdAt: a.datetime(),
})
.**disableOperations**(["mutations"])
.identifier(["id"])
.secondaryIndexes((index) => [index("userAlias").sortKeys(["dashboardId"])])
.authorization((allow) => allow.authenticated()),

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