Upload Thumbnail

JSON body for PUT /maps/{map_id}/thumbnail/.

Replaces a previous text/plain body shape that openapi-python-client could not parse (would silently skip endpoint).

data_uri carries explicit length bounds so Pydantic surfaces a 422 with field-level detail (better SDK-consumer UX than a generic 400) and the OpenAPI schema documents the limit. The router still validates the data:image/ prefix and base64 encoding; those are content-shape checks Pydantic length cannot cover.

• min_length=22: a minimal valid prefix is data:image/x;base64, (20 chars) plus at least one payload byte (e.g., data:image/x;base64,XX). Use 22 as a pragmatic floor that rejects empty / clearly-malformed values without false-positives on the smallest legitimate payloads.
• max_length=100_000: matches the previous router-side 100KB cap.