Package Management

[AttilaMihaly]

The Morphir IR included the concept of packages and provided the ability to cross-reference types and values between
them since it was first open-sourced. For now the only external package the tools allow you to reference though is
the SDK which is built-in. Changing that to be able to depend on user-defined packages has been on our backlog for some
time, and the introduction of decorations makes it even more timely to look into package management.

Package management is a large and complex topic, so we will take a gradual approach to defining our solution. In-line
with Morphir's philosophy, we will try hard to avoid inventing new things unless necessary and will reuse as much of
the great package management solutions out there as possible. Before we get into that though let's start by clarifying
what the package manager will do.

User Stories

Morphir IR related

1. As a Morphir author, I want to publish a Morphir IR to a central repository so that the types and values defined in
   it can be used in other Morphir IRs.
2. As a Morphir author, I want to use types and values from other published packages so that I don't have to redefine
   or copy them in my project.
3. As a Morphir author, I want published Morphir IRs to be versioned so that I can make changes to them without breaking
   consumers.

Decoration related

1. As a Morphir author, I want to publish a decoration schema to a central repository so that it
   can be used by authors to decorate Morphir IRs based on it.
2. As a Morphir author, I want to publish a decoration schema to a central repository so that it can be used to
   implement tools (such as backends) that process those decorations.
3. As a Morphir author, I want to use published decoration schemas add decoration instances to my package so that I can
   provide extra information for the tools that require them.
4. As a Morphir author, I want to publish a decoration instance attached to my package or another package that I defined
   as a dependency so that it can be used by tools that require them.
5. As a Morphir backend developer, I want to use published decoration schemas to define the input for my backend so
   that I can reliably process them.
6. As a Morphir author, I want published decoration schemas to be versioned so that I can make changes to them without
   breaking tools that process them.
7. As a Morphir author, I want published decoration instances to refer to a specific decoration schema version so that
   schema changes don't break the instances.
8. As a Morphir backend developer, I want to declare which specific version of a decoration schema a backend expects so
   that changes in the schema that causes decoration instances to change in structure doesn't cause runtime errors while processing the decoration in the backend.