Create a sequence diagram for sending a message from CRM for task 4.

A sequence diagram for sending a message from CRM describes the interaction between system components during message transmission.

Main participants:

• User
• CRM system
• Message sending service
• External system (e.g., Email/SMS gateway)

Example sequence:

1. User initiates message sending in CRM.
2. CRM validates message data.
3. CRM sends a request to the Message Service.
4. Message Service receives the request and forms the message.
5. Message Service sends the message to the external system.
6. External system confirms receipt.
7. Message Service returns the status to CRM.
8. CRM displays the result to the user.

Such a diagram is conveniently drawn in UML editors, for example, draw.io or PlantUML.

Example PlantUML code for the diagram:

@startuml
actor User
participant CRM
participant "Message Service" as MS
participant "External System" as ES

User -> CRM: Initiate message sending
CRM -> CRM: Validate data
CRM -> MS: Send sending request
MS -> MS: Form the message
MS -> ES: Send message
ES --> MS: Confirm receipt
MS --> CRM: Sending status
CRM --> User: Display result
@enduml

This diagram clearly shows the message flow and component interaction during message sending from CRM.