add update customer company docs

_snippets/graphql/update-customer-company.mdx

@@ -0,0 +1,40 @@
+```graphql Mutation
+mutation updateCustomerCompany(
+  $customerId: ID!, 
+  $companyId: ID!, 
+  $companyDomainName: String!
+) {
+  updateCustomerCompany(
+    input: {
+      customerId: $customerId, 
+      companyIdentifier: {
+        companyId: $companyId, 
+        companyDomainName: $companyDomainName
+      }
+    }
+  ) {
+    customer {
+      id
+      company {
+        id
+        name
+        logoUrl
+        domainName
+      }
+    }
+    error {
+      message
+      type
+      code
+    }
+  }
+}
+```
+
+```json Variables
+{
+  "customerId": "c_01H14DFQ4PDYBH398J1E99TWSS",
+  "companyId": "co_01HRRMRPERZCK42HTPD4JQ57NB",
+  "companyDomainName": "nike.com"
+}
+```

api-reference/graphql/companies.mdx

@@ -7,4 +7,4 @@ Companies allow you to identify which company a customer is part of. Plain autom
 
 A customer can only belong to a single company.
 
-Apart from seeing which company a customer is part of, you can also list all customers associated to a given company.
+Apart from seeing which company a customer is part of, you can also list all companies you've interacted with.

api-reference/graphql/companies/update-customer-company.mdx

@@ -3,20 +3,21 @@ title: 'Update customer company'
 sidebarTitle: 'Update customer company'
 ---
 
-You can add a customer to multiple tenants.
+Plain automatically derived a customer's company for you, but you can also update it manually.
 
-When selecting the customer you can chose how to identify them. You can use the customer's email, externalId or id.
+Both customer and company are identified by their Plain ids (respectively, `c_...` and `co_...`).
+
+If you wish to only remove the customer's associated company, then you can pass `null` as the `companyIdentifier`.
 
 For this mutation you need the following permissions:
 
-- `TODO`
-- `TODO`
+- `customer:edit`
 
 <Tabs>
   <Tab title="Typescript SDK">
-    <Snippet file="typescript-sdk/add-customer-to-tenants.mdx" />
+    <Snippet file="typescript-sdk/update-customer-company.mdx" />
   </Tab>
   <Tab title="GraphQL">
-    <Snippet file="graphql/add-customer-to-tenants.mdx" />
+    <Snippet file="graphql/update-customer-company.mdx" />
   </Tab>
 </Tabs>