Lucas/t 231 timebox i can create a company at the same time im creating (#140)

This PR is a bit messy:

adding graphql schema
adding create company creation on company select on People page
some frontend refactoring to be continued

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Co-authored-by: Charles Bochet <charles@twenty.com>

front/src/pages/companies/companies-columns.tsx

@@ -161,7 +161,7 @@ export const useCompaniesColumns = () => {
                 name: accountOwner.displayName || '',
               };
             }}
-            changeHandler={(relation: User) => {
+            onChange={(relation: User) => {
               const company = props.row.original;
               if (company.accountOwner) {
                 company.accountOwner.id = relation.id;