1774 extensibility v1 create an exhaustive documentation readme or dedicated section in twenty contributing doc (#16751)

As title

<img width="1108" height="894" alt="image"
src="https://github.com/user-attachments/assets/e2dc7e12-72e3-4ca3-ac7b-a94de547f82a"
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packages/twenty-server/src/engine/metadata-modules/flat-role/utils/from-create-role-input-to-flat-role-to-create.util.ts

@@ -44,8 +44,6 @@ export const fromCreateRoleInputToFlatRoleToCreate = ({
     canBeAssignedToUsers: createRoleInput.canBeAssignedToUsers ?? true,
     canBeAssignedToAgents: createRoleInput.canBeAssignedToAgents ?? true,
     canBeAssignedToApiKeys: createRoleInput.canBeAssignedToApiKeys ?? true,
-    canBeAssignedToApplications:
-      createRoleInput.canBeAssignedToApplications ?? true,
     isEditable: true,
     workspaceId,
     createdAt: now,

packages/twenty-server/src/engine/metadata-modules/flat-role/utils/from-role-entity-to-flat-role.util.ts

@@ -18,7 +18,6 @@ export const fromRoleEntityToFlatRole = (role: RoleEntity): FlatRole => {
     canBeAssignedToUsers: role.canBeAssignedToUsers,
     canBeAssignedToAgents: role.canBeAssignedToAgents,
     canBeAssignedToApiKeys: role.canBeAssignedToApiKeys,
-    canBeAssignedToApplications: role.canBeAssignedToApplications,
     workspaceId: role.workspaceId,
     createdAt: role.createdAt.toISOString(),
     updatedAt: role.updatedAt.toISOString(),