schema: make user fields non-nullable

They can always be empty. This simplifies mutation, since graphql_client
doesn't have an easy way to conditionally leave out fields (we could do
that with `@include`, but that's one bool per field in addition to the
field, a bit ugly).

server/src/domain/handler.rs

@@ -8,9 +8,9 @@ use std::collections::HashSet;
 pub struct User {
     pub user_id: String,
     pub email: String,
-    pub display_name: Option<String>,
-    pub first_name: Option<String>,
-    pub last_name: Option<String>,
+    pub display_name: String,
+    pub first_name: String,
+    pub last_name: String,
     // pub avatar: ?,
     pub creation_date: chrono::DateTime<chrono::Utc>,
 }
@@ -21,9 +21,9 @@ impl Default for User {
         User {
             user_id: String::new(),
             email: String::new(),
-            display_name: None,
-            first_name: None,
-            last_name: None,
+            display_name: String::new(),
+            first_name: String::new(),
+            last_name: String::new(),
             creation_date: chrono::Utc.timestamp(0, 0),
         }
     }

server/src/domain/sql_backend_handler.rs

@@ -3,7 +3,7 @@ use crate::infra::configuration::Configuration;
 use async_trait::async_trait;
 use futures_util::StreamExt;
 use futures_util::TryStreamExt;
-use sea_query::{Expr, Iden, Order, Query, SimpleExpr, Value};
+use sea_query::{Expr, Iden, Order, Query, SimpleExpr};
 use sqlx::Row;
 use std::collections::HashSet;
 
@@ -179,9 +179,9 @@ impl BackendHandler for SqlBackendHandler {
         let values = vec![
             request.user_id.clone().into(),
             request.email.into(),
-            request.display_name.map(Into::into).unwrap_or(Value::Null),
-            request.first_name.map(Into::into).unwrap_or(Value::Null),
-            request.last_name.map(Into::into).unwrap_or(Value::Null),
+            request.display_name.unwrap_or_default().into(),
+            request.first_name.unwrap_or_default().into(),
+            request.last_name.unwrap_or_default().into(),
             chrono::Utc::now().naive_utc().into(),
         ];
         let query = Query::insert()

server/src/domain/sql_tables.rs

@@ -49,9 +49,13 @@ pub async fn init_table(pool: &Pool) -> sqlx::Result<()> {
                     .primary_key(),
             )
             .col(ColumnDef::new(Users::Email).string_len(255).not_null())
-            .col(ColumnDef::new(Users::DisplayName).string_len(255))
-            .col(ColumnDef::new(Users::FirstName).string_len(255))
-            .col(ColumnDef::new(Users::LastName).string_len(255))
+            .col(
+                ColumnDef::new(Users::DisplayName)
+                    .string_len(255)
+                    .not_null(),
+            )
+            .col(ColumnDef::new(Users::FirstName).string_len(255).not_null())
+            .col(ColumnDef::new(Users::LastName).string_len(255).not_null())
             .col(ColumnDef::new(Users::Avatar).binary())
             .col(ColumnDef::new(Users::CreationDate).date_time().not_null())
             .col(ColumnDef::new(Users::PasswordHash).binary())