More simplified UX

[shizhMSFT]

A common scenario is to get content such as manifest and blob into the memory for further processing.

Although the Resolve() and Fetch() methods in the Target interface provides a simple clean secure way to read content, we still need a simplier UX such as GetManifest() and GetBlob() (or can be further combined as GetContent()). Similarly, we might also need PutContent() in the oras package.

[sajayantony]

We should start discussing an RC bar at this point and once that is release update notation, ratify and other projects like oras CLI.

[shizhMSFT]

An interesting user case can be found at #22

[Wwwsylvia]

This one might be useful - https://github.com/oras-project/oras-go/pull/182#discussion_r899787777

[Wwwsylvia]

Related discussion: #240

[Wwwsylvia]

Based on the discussion, I will break down this issue into several sub-tasks and will send PRs separately.

• [x] #272
• [x] #273
• [x] #274
• [x] #275

[Wwwsylvia]

Closing as all sub-tasks are done.