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"
/>

packages/twenty-server/src/engine/metadata-modules/role/dtos/create-role-input.dto.ts

@@ -70,9 +70,4 @@ export class CreateRoleInput {
   @IsOptional()
   @Field({ nullable: true })
   canBeAssignedToApiKeys?: boolean;
-
-  @IsBoolean()
-  @IsOptional()
-  @Field({ nullable: true })
-  canBeAssignedToApplications?: boolean;
 }

packages/twenty-server/src/engine/metadata-modules/role/dtos/update-role-input.dto.ts

@@ -71,11 +71,6 @@ export class UpdateRolePayload {
   @IsOptional()
   @Field({ nullable: true })
   canBeAssignedToApiKeys?: boolean;
-
-  @IsBoolean()
-  @IsOptional()
-  @Field({ nullable: true })
-  canBeAssignedToApplications?: boolean;
 }
 
 @InputType()

packages/twenty-server/src/engine/metadata-modules/role/role.entity.ts

@@ -73,9 +73,6 @@ export class RoleEntity extends SyncableEntity implements Required<RoleEntity> {
   @Column({ nullable: false, default: true })
   canBeAssignedToApiKeys: boolean;
 
-  @Column({ nullable: false, default: true })
-  canBeAssignedToApplications: boolean;
-
   @OneToMany(
     () => RoleTargetEntity,
     (roleTargets: RoleTargetEntity) => roleTargets.role,