Add entity for reserved list

[hstonec]

This PR added the Cloud SQL entity for reserved list.

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This change is 

[CydeWeys]

+reviewer:@gbrodman

Reviewable status: 0 of 6 files reviewed, all discussions resolved (waiting on @CydeWeys and @gbrodman)

[CydeWeys]

Reviewable status: 0 of 6 files reviewed, all discussions resolved (waiting on @gbrodman)

[gbrodman]

Reviewable status: 0 of 6 files reviewed, 2 unresolved discussions (waiting on @gbrodman and @hstonec)

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core/src/main/java/google/registry/schema/tld/ReservedList.java, line 127 at r1 (raw file):

  public Long getRevisionId() {
    checkState(
        revisionId != null, "revisionId is null because it is not persisted in the database");

nit, something like "revisionId is null because this object has not been persisted to the database yet"

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core/src/main/java/google/registry/schema/tld/ReservedList.java, line 137 at r1 (raw file):

  /** Returns a {@link Map} of domain labels to {@link ReservedEntry}. */
  public Map<String, ReservedEntry> getLabelsToReservations() {

nit: wrap in ImmutableMap?

[hstonec]

Reviewable status: 0 of 6 files reviewed, all discussions resolved

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core/src/main/java/google/registry/schema/tld/ReservedList.java, line 127 at r1 (raw file):

Previously, gbrodman wrote…

nit, something like "revisionId is null because this object has not been persisted to the database yet"

Done.

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core/src/main/java/google/registry/schema/tld/ReservedList.java, line 137 at r1 (raw file):

Previously, gbrodman wrote…

nit: wrap in ImmutableMap?

Done.