Give every IP lookup result the same fields (closes #200)

Every result of /ip/, /ip/{addr} and /api/v1/ip/{ip} now has every
field. A field without a value is null instead of left out, so an
address with no live route has all its route and AS fields set to null.
ptr is an empty list when there are no PTR names.

Two new fields, num_origins and origin_asns, give how many origin ASes
peers carry the netblock with, and which. The routing table's prefix
summary now lists them. asn still names the origin that most peers
carry.

first_seen is null, no longer the zero time, when the database has not
stored the netblock yet.

Model: opus-5-5

internal/server/models.go

@@ -38,30 +38,37 @@ type PrefixDistribution struct {
 	Count      int `json:"count"`
 }
 
-// IPInfo represents comprehensive IP information for the /ip endpoint
+// IPInfo is what the IP lookup knows about the route of an address and that
+// route's origin AS. A field is nil, null in JSON, when its value is not known.
+// Every field is nil for an address with no route.
 //
 //nolint:tagliatelle // field names are the existing JSON API
 type IPInfo struct {
-	IP         string `json:"ip"`
-	Netblock   string `json:"netblock"`
-	MaskLength int    `json:"mask_length"`
-	IPVersion  int    `json:"ip_version"`
-	NumPeers   int    `json:"num_peers"`
-	// AS information
-	ASN         int    `json:"asn"`
-	ASName      string `json:"as_name,omitempty"`
-	Handle      string `json:"handle,omitempty"`
-	Description string `json:"description,omitempty"`
-	OrgName     string `json:"org_name,omitempty"`
-	OrgID       string `json:"org_id,omitempty"`
-	Address     string `json:"address,omitempty"`
-	CountryCode string `json:"country_code,omitempty"`
-	AbuseEmail  string `json:"abuse_email,omitempty"`
-	RIR         string `json:"rir,omitempty"`
-	// Timestamps. LastSeen is zero, and left out of JSON, when the prefix
-	// keeps no route.
-	FirstSeen time.Time `json:"first_seen"`
-	LastSeen  time.Time `json:"last_seen,omitzero"`
+	// Netblock is the most specific prefix that holds the address.
+	Netblock   *string `json:"netblock"`
+	MaskLength *int    `json:"mask_length"`
+	IPVersion  *int    `json:"ip_version"`
+	NumPeers   *int    `json:"num_peers"`
+	// ASN is the origin AS that the most peers carry the netblock with.
+	ASN *int `json:"asn"`
+	// NumOrigins and OriginASNs are how many origin ASes peers carry the
+	// netblock with, and which, in AS number order.
+	NumOrigins *int  `json:"num_origins"`
+	OriginASNs []int `json:"origin_asns"`
+	// The details the database holds about the AS in ASN.
+	ASName      *string `json:"as_name"`
+	Handle      *string `json:"handle"`
+	Description *string `json:"description"`
+	OrgName     *string `json:"org_name"`
+	OrgID       *string `json:"org_id"`
+	Address     *string `json:"address"`
+	CountryCode *string `json:"country_code"`
+	AbuseEmail  *string `json:"abuse_email"`
+	RIR         *string `json:"rir"`
+	// FirstSeen is when RouteWatch first saw the netblock. LastSeen is the
+	// time of the netblock's newest kept route.
+	FirstSeen *time.Time `json:"first_seen"`
+	LastSeen  *time.Time `json:"last_seen"`
 	// Indicates if WHOIS data needs refresh (not serialized)
 	NeedsWHOISRefresh bool `json:"-"`
 }