Update API format and support multiple string/pre-extracted inputs

[danmichaeljones]

Update serialisation to use new API input format and support multiple string/pre-extracted inputs.

• The "simple" adds (using python types for string / conversation) work same as before
• Adding StringContent has been extended to also support content: list[str]

client.memories.add(
    StringContent(content=["User prefers dark mode.", "User likes pizza."]),
    user_id="...",
)

• The pre-extracted data type has been (non-backwards-compatibly) updated so that PreExtractedContent contains list[PreExtractedItem].

client.memories.add(
    PreExtractedContent(items=[
        PreExtractedItem(content="User prefers dark mode.", topic="UserKnowledge"),
        PreExtractedItem(content="User likes pizza.", topic="UserKnowledge"),
    ]),
    user_id="...",
)

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

[augustas1]

feels like content inside content.
Maybe all our dataclasses should be renamed to input, and content would refer only to the atomic part (the actual texts)?

[danmichaeljones]

Good shout - I've renamed content to input throughout so that content now only refers to the inner fields. I also updated the .add() arg/type alias to input_data: AddInput to match (but not shadow input builtin)