Docs for trial lead flow

doc/development/product_qualified_lead_guide/index.md

@@ -92,7 +92,48 @@ The flow of a PQL lead is as follows:
 1. Marketo does scoring and sends the form to Salesforce.
 1. Our Sales team uses Salesforce to connect to the leads.
 
-### Lead flow on GitLab.com
+### Trial lead flow 
+
+#### Trial lead flow on GitLab.com
+
+```mermaid
+sequenceDiagram
+    Trial Frontend Forms ->>TrialsController#create_lead: GitLab.com frontend sends [lead] to backend
+    TrialsController#create_lead->>CreateLeadService: [lead]
+    TrialsController#create_lead->>ApplyTrialService: [lead] Apply the trial
+    CreateLeadService->>SubscriptionPortalClient#generate_trial(sync_to_gl=false): [lead] Creates customer account on CustomersDot
+    ApplyTrialService->>SubscriptionPortalClient#generate_trial(sync_to_gl=true): [lead] Asks CustomersDot to apply the trial on namespace
+    SubscriptionPortalClient#generate_trial(sync_to_gl=false)->>CustomersDot|TrialsController#create(sync_to_gl=false): GitLab.com sends [lead] to CustomersDot
+    SubscriptionPortalClient#generate_trial(sync_to_gl=true)->>CustomersDot|TrialsController#create(sync_to_gl=true): GitLab.com asks CustomersDot to apply the trial
+
+
+```
+
+#### Trial lead flow on CustomersDot (sync_to_gl)
+
+```mermaid
+sequenceDiagram
+    CustomersDot|TrialsController#create->>HostedPlans|CreateTrialService#execute: Save [lead] to leads table for monitoring purposes
+    HostedPlans|CreateTrialService#execute->>BaseTrialService#create_account: Creates a customer record in customers table
+    HostedPlans|CreateTrialService#create_platypus_lead->>PlatypusLogLeadService: Creates a platypus lead
+    HostedPlans|CreateTrialService#create_platypus_lead->>Platypus|CreateLeadWorker: Async worker to submit [lead] to Platypus
+    Platypus|CreateLeadWorker->>Platypus|CreateLeadService: [lead]
+    Platypus|CreateLeadService->>PlatypusApp#post: [lead]
+    PlatypusApp#post->>Platypus: [lead] is sent to Platypus
+```
+
+#### Applying the trial to a namespace on CustomersDot
+
+```mermaid
+sequenceDiagram
+    HostedPlans|CreateTrialService->load_namespace#Gitlab api/namespaces: Load namespace details
+    HostedPlans|CreateTrialService->create_order#: Creates an order in orders table
+    HostedPlans|CreateTrialService->create_trial_history#: Creates a record in trial_histories table
+```
+
+### Hand raise lead flow 
+
+#### Hand raise flow on GitLab.com
 
 ```mermaid
 sequenceDiagram
@@ -100,9 +141,9 @@ sequenceDiagram
     TrialsController#create_hand_raise_lead->>CreateHandRaiseLeadService: [lead]
     CreateHandRaiseLeadService->>SubscriptionPortalClient: [lead]
     SubscriptionPortalClient->>CustomersDot|TrialsController#create_hand_raise_lead: GitLab.com sends [lead] to CustomersDot
-```      
+```
 
-### Lead flow on CustomersDot and later
+#### Hand raise flow on CustomersDot
 
 ```mermaid
 sequenceDiagram
@@ -111,9 +152,9 @@ sequenceDiagram
     Platypus|CreateLeadWorker->>Platypus|CreateLeadService: [lead]
     Platypus|CreateLeadService->>PlatypusApp#post: [lead]
     PlatypusApp#post->>Platypus: [lead] is sent to Platypus
-```      
+```
 
-### Lead flow after Platypus
+### PQL flow after Platypus for all lead types
 
 ```mermaid
 sequenceDiagram