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Core App

The core app provides foundational infrastructure used by all other apps in the Maybern backend. It includes base models, custom field types, API utilities, and common services.

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Base Models

All models in Maybern inherit from one of these base classes:
ModelDescription
TimeStampedModelAdds created_at and updated_at fields
CustomerTimeStampedModelAdds customer_id for multi-tenancy
AuditableModelEnables audit logging for changes
VersionModelFor type-2 versioned entities
from server.apps.core.models.customer_time_stamped import CustomerTimeStampedModel

class MyEntity(CustomerTimeStampedModel):
    name = model_fields.TextModelField()
    # customer_id, created_at, updated_at are automatic

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Custom Field Types

All ORM fields are wrapped in server.apps.core.models.fields for additional functionality:
  • MUUIDField - UUID with prefix (e.g., INVS_abc123)
  • TextModelField - Text with validation
  • ForeignKeyModelField - FK with sensible defaults
  • DecimalModelField - Decimal with precision
  • DateModelField - Date field
  • BooleanModelField - Boolean field

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Field Decorators

from server.apps.core.models.decorators import sensitive, encrypt

class User(CustomerTimeStampedModel):
    @sensitive
    ssn = model_fields.TextModelField()  # Masked in logs
    
    @encrypt
    api_key = model_fields.TextModelField()  # Encrypted at rest

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API Utilities

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Request Context

The RequestCtx dataclass contains request-scoped information: 
@dataclass
class RequestCtx:
    customer_id: MUUID
    user_id: MUUID
    request_source: RequestSource
    feature_flags: list[str]

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API Decorators

from server.apps.core.decorators.api import api_get, api_post

class MyAPI(GetAPIView, PostAPIView):
    @api_get(
        operation_id=OperationIds.MY_APP.value.GET_ENTITY,
        response=EntityResponse,
        description="Get an entity",
    )
    def get(self, *, url_params, ctx, param_data):
        return MyService.get_entity(ctx=ctx, entity_id=url_params["entity_id"])

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Core Services

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Cache Service

Distributed caching using Redis: 
from server.apps.core.services.cache import CacheService

# Set a value
CacheService.set(key="my_key", value=data, ttl=3600)

# Get a value
data = CacheService.get(key="my_key")

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Evaluate Expression Service

Execute dynamic calculations: 
from server.apps.core.services.evaluate import EvaluateExpressionService

result = EvaluateExpressionService.evaluate(
    expression="value * rate",
    context={"value": 100, "rate": 0.05}
)

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I18n Service

Internationalization support: 
from server.apps.core.services.i18n import I18nService

translated = I18nService.translate(
    key="fee_types.management_fee",
    locale="en"
)

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Generate MUUID Service

Create prefixed UUIDs: 
from server.apps.core.services.muuid import GenerateMUUIDService

entity_id = GenerateMUUIDService.generate(prefix="ENTY")
# Returns: MUUID("ENTY_abc123...")

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Rounding Service

Consistent rounding strategies: 
from server.apps.core.services.rounding import RoundingService

rounded = RoundingService.round_to_cents(
    value=Decimal("100.555"),
    strategy=RoundingStrategy.HALF_UP
)

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Managers and QuerySets

Custom managers wrap Django ORM functionality:
  • BaseTimeStampedModelManager - Core querying logic
  • TimeStampedModelManager - For non-tenant models
  • CustomerTimeStampedModelManager - Adds customer filtering
  • VersionableModelManager - For versioned models
# Customer filtering is automatic
entities = MyEntity.objects.filter(ctx=ctx, name="Test")

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Constraints

Custom database constraints: 
from server.apps.core.models.constraints import require_exactly_one_non_null_constraint

class Override(CustomerTimeStampedModel):
    user = models.ForeignKey(User, null=True)
    customer = models.ForeignKey(Customer, null=True)
    
    class Meta:
        constraints = [
            require_exactly_one_non_null_constraint(
                fields=["user", "customer"],
                name="exactly_one_target",
            ),
        ]

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Exceptions

Standard exception types: 
from server.apps.core.exceptions import MaybernError, MaybernExpectedUserError

# Internal system error
raise MaybernError("Database connection failed")

# User-facing error
raise MaybernExpectedUserError("Please provide a valid date")

Models & Migrations

Model design patterns and migrations.

API Development

Building APIs with the core decorators.