Can't run 'dotnet ef database update' because of insufficient privileges

I am at a confusing standstill with developing my .NET application and setting up the database.

I am using a docker container image of mssql/sql-express. I've got it running and can log into the sys admin account.

I created a login CommanderApi, database CommanderDb and created a user in that database with the CommanderApi login. Then I created an initial migration, and the update fails when I try to run it.

Is there something wrong with my approach? It seems that the design idea behind using a framework and entity is it takes a lot of the boilerplate SQL code out of the programmers hands. However, the tutorial video I'm watching, they use SSMS and do all the steps I described above - minus one step - giving the user credentials which my .NET application's connection string logs into the sufficient permissions.

When I try to manually give the CommanderApi user permissions to edit the database, I keep getting syntax errors:

Changed database context to 'CommanderDb'.  
 1> grant all on CommanderDb to 'CommanderApi'  
 2> go

Msg 102, Level 15, State 1, Server f69fca1fbe0b, Line 1
Incorrect syntax near 'CommanderApi'

1> grant all on CommanderDb to 'CommanderApi'@'localhost'
2> go

Msg 102, Level 15, State 1, Server f69fca1fbe0b, Line 1
Incorrect syntax near 'CommanderApi'

1> grant all on CommanderDb to CommanderApi
2> go

Msg 15151, Level 16, State 1, Server f69fca1fbe0b, Line 1
Cannot find the object 'CommanderDb', because it does not exist or you do not have permission.

mssql@f69fca1fbe0b:/$ /opt/mssql-tools/bin/sqlcmd -S localhost -U sa -P super_DUPER_password
1> grant all on CommanderDb to 'CommanderApi'@'localhost'
2> go

Msg 102, Level 15, State 1, Server f69fca1fbe0b, Line 1
Incorrect syntax near 'CommanderApi'.

1> grant all on CommanderDb to CommanderApi@localhost
2> go

Msg 15151, Level 16, State 1, Server f69fca1fbe0b, Line 1
Cannot find the object 'CommanderDb', because it does not exist or you do not have permission.

1> delete CommanderDb
2> go

Msg 208, Level 16, State 1, Server f69fca1fbe0b, Line 1
Invalid object name 'CommanderDb'.

1> drop CommanderDb
2> go

Msg 343, Level 15, State 1, Server f69fca1fbe0b, Line 1
Unknown object type 'CommanderDb' used in a CREATE, DROP, or ALTER statement.

1> drop 'CommanderDb'
2> go

Msg 102, Level 15, State 1, Server f69fca1fbe0b, Line 1
Incorrect syntax near 'CommanderDb'.

1> drop database if exists 'CommanderDb'
2> go

Msg 102, Level 15, State 1, Server f69fca1fbe0b, Line 1
Incorrect syntax near 'CommanderDb'.

1> drop database if exists CommanderDb
2> go
1> exit

Error I get when trying to run dotnet ef database update

C:\Users\Ben\VsCode\.net\angular_template\commander>dotnet ef database update
Build started...
Build succeeded.

fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
Failed executing DbCommand (28ms) [Parameters=[], CommandType='Text', CommandTimeout='60']
CREATE DATABASE [CommanderDb];
Failed executing DbCommand (28ms) [Parameters=[], CommandType='Text', CommandTimeout='60']
CREATE DATABASE [CommanderDb];
Microsoft.Data.SqlClient.SqlException (0x80131904): CREATE DATABASE permission denied in database 'master'.

at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action1 wrapCloseInAction) at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action1 wrapCloseInAction)
at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
at Microsoft.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean isAsync, Int32 timeout, Boolean asyncWrite)
at Microsoft.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(TaskCompletionSource1 completion, Boolean sendToPipe, Int32 timeout, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String methodName) at Microsoft.Data.SqlClient.SqlCommand.ExecuteNonQuery() at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteNonQuery(RelationalCommandParameterObject parameterObject) at Microsoft.EntityFrameworkCore.Migrations.MigrationCommand.ExecuteNonQuery(IRelationalConnection connection, IReadOnlyDictionary2 parameterValues)
at Microsoft.EntityFrameworkCore.Migrations.Internal.MigrationCommandExecutor.ExecuteNonQuery(IEnumerable`1 migrationCommands, IRelationalConnection connection)
at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerDatabaseCreator.Create()
at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.Migrate(String targetMigration)
at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.UpdateDatabase(String targetMigration, String connectionString, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabaseImpl(String targetMigration, String connectionString, String contextType)
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.UpdateDatabase.<>c__DisplayClass0_0.<.ctor>b__0()
at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)

ClientConnectionId:d2819228-4d75-47ee-92f4-da88caa6a18f
Error Number:262,State:1,Class:14
CREATE DATABASE permission denied in database 'master'.

C:\Users\Ben\VsCode.net\angular_template\commander>docker exec -it sql-server-db "bash"
mssql@f69fca1fbe0b:/$ /opt/mssql-tools/bin/sqlcmd -S localhost -U CommanderApi -P Commander9
Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server : Cannot open user default database. Login failed..
Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server : Login failed for user 'CommanderApi'..
mssql@f69fca1fbe0b:/$ /opt/mssql-tools/bin/sqlcmd -S localhost -U SA -P super_Duper_password
Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server : Login failed for user 'SA'..
mssql@f69fca1fbe0b:/$ /opt/mssql-tools/bin/sqlcmd -S localhost -U sa -P super_Duper_password
Sqlcmd: Error: Microsoft ODBC Driver 17 for SQL Server : Login failed for user 'sa'..
mssql@f69fca1fbe0b:/$ /opt/mssql-tools/bin/sqlcmd -S localhost -U SA -P super_DUPER_password

Does anybody know what I am doing wrong? Appreciate any help.

my docker-compose.yml

version: "3.7"
services:
  sql-server-db:
    container_name: sql-server-db
    image: mcr.microsoft.com/mssql/server:2019-latest
    ports:
      - "1433:1433"
    environment:
      SA_PASSWORD: "super_DUPER_password"
      ACCEPT_EULA: "Y"

probably evident but this is a non production mode application, so none of the credentials are valid/ secure

startup.cs section were we add the db context with D/I

services.AddDbContext<CommanderContext>(options => options.UseSqlServer
                (Configuration.GetConnectionString("DefaultConnection")));

connection string

"ConnectionStrings" : 
{   
    "DefaultConnection" : "Server=localhost,1433;Initial Catalog=CommanderDb;User ID=CommanderApi;Password=Commander9;"
}